Fix key extraction for z{union,inter}store
Fix key extraction for z{union,inter}store

The previous implementation wasn't taking into account
the storage key in position 1 being a requirement (it
was only counting the source keys in positions 3 to N).

Fixes antirez/redis#1581

itamarhaber/redis,brg-liuwei/redis,190235047/redis,tanghaodong25/redis,yossigo/redis,hawkchch/redis,nuxeh/redis,wenxueliu/redis_comment,netroby/redis,arijitvt/redis,mverrilli/redis,csuhawk/redis,ouyangkongtong/redis,MOON-CLJ/redis,flashbuckets/redis,oranagra/redis,citusdata/redis,gilala/hredis,AplayER/redis,cloudrain21/redis,modulexcite/redis,guker/redis,j0hnma/hszredis,cloudrain21/redis,mcanthony/redis,qiyang0221/redis,linfangrong/redis,arijitvt/redis,davidradunz/redis,nnog/redis,Wangyao14cyy/redis,weizijun/redis,rogerlz/redis,mcanthony/redis,rouzier/redis,pedigree/redis,pmem/redis,qiyang0221/redis,yuhc/redis-benchmark-enhanced,riyan8250/redis,soloestoy/redis,mgk/redis,atreeyang/redis,universsky/redis,gilala/hbjredis,Aaron1992/redis,soloestoy/redis,kaushik94/redis,nuxeh/redis,kmiku7/redis,blackmady/redis,oranagra/redis,mgk/redis,seandsky/redis,zczhuohuo/redis,YuanZhewei/redis,Aaron1992/redis,pmem/redis,AALEKH/redis,190235047/redis,izhoujie/redis,mingyaaaa/redis,honestme/redis,Aliceljm1/redis,z-fork/redis,OmarQunsul/graph-redis,itugs/redis,NBSW/redis,wprice/redis,davidradunz/redis,holstvoogd/redis,GrimDerp/redis,seandsky/redis,itugs/redis,devaos/redis,healerkx/redis,Wangyao14cyy/redis,wujf/redis,weizijun/redis,StevenTsai/redis,LongXQ/redis,charsyam/redis,duanx/redis,mengzhejin/RedisStudy,harrisonfeng/redis,atreeyang/redis,zhiliaoniu/redis,mumingv/redis,hedisdb/hedis,GitHubMota/redis,wenxueliu/redis_comment,devaos/redis,rogerlz/redis,yossigo/redis,mattsta/redis,josiahcarlson/redis,rogerchina/redis,seppo0010/rlite-server,csuhawk/redis,Aliceljm1/redis,simplestbest/redis,citusdata/redis,july2993/redis,MasahikoSawada/redis,YuanZhewei/redis,j0hnma/hszredis,shreesundara/redis,jingjidejuren/redis,jbochi/redis,timothyohare/3rdPartySrc-redis,gilala/redis,PKRoma/redis,YuraLukashik/redis,twskipper/redis,xlzhan/redis,pkdevbox/redis,ipmobiletech/redis,colstrom/redis,dreamquster/redis,CodeJuan/redis,gaoxianglong/redis,CodeJuan/redis,gilala/bjredis,tanghaodong25/redis,weizijun/redis,cloudrain21/redis,zhcy/redis,z-fork/redis,roth1002/redis,gaoxianglong/redis,supasate/redis,rogerchina/redis,mengyou0304/redis,francischan714/redis,qiyang0221/redis,mingyaaaa/redis,kensou97/redis,ytjiang/redis,gaoxianglong/redis,iandyh/redis,spinlock/redis,oranagra/redis,guker/redis,gilala/redis,simplestbest/redis,hawkchch/redis,ofirluzon/redis,mverrilli/redis,cnbin/redis,july2993/redis,4396/redis,dayuoba/redis,taoguan/redis,abhiklodh/redis,taoguan/redis,Sciumo/redis,pmem/redis,cusspvz/redis,spinlock/redis,takeshineshiro/redis,tjschuck/redis,july2993/redis,timothyohare/3rdPartySrc-redis,SyntaxStacks/redis,Markgorden/redis,a-pavlov/redis,janekmi/redis,citusdata/redis,twskipper/redis,Markgorden/redis,hgl888/redis,zhiliaoniu/redis,gilala/hbjredis,JoeWoo/redis,mengyou0304/redis,kensou97/redis,wprice/redis,kaushik94/redis,gilala/bjredis,mengyou0304/redis,josiahcarlson/redis,flashbuckets/redis,allengaller/redis,kmiku7/redis,pmem/redis,programmecat/redis,valdsJohn/redis,RepmujNetsik/redis,soveran/redis,gilala/hbjredis,alenslan/redis,yossigo/redis,YuraLukashik/redis,ipmobiletech/redis,atreeyang/redis,shreesundara/redis,yossigo/redis,davidradunz/redis,seppo0010/redis,gilala/hredis,gilala/redis,hawkchch/redis,PradheepShrinivasan/redis,seppo0010/redis,zczhuohuo/redis,sunheehnus/redis,ituncle/redis,netroby/redis,alenslan/redis,spinlock/redis,PKRoma/redis,jbochi/parallel_redis,RepmujNetsik/redis,ctripcorp/redis,OmarQunsul/graph-redis,cnbin/redis,ErikDubbelboer/redis,kmiku7/redis,healerkx/redis,ncopa/redis,simplestbest/redis,mengzhejin/RedisStudy,wbailey5/redis,4396/redis,tanghaodong25/redis,aim-for-better/redis,GrimDerp/redis,wprice/redis,universsky/redis,fengshao0907/redis,jbochi/parallel_redis,mverrilli/redis,universsky/redis,NBSW/redis,ton31337/redis,cusspvz/redis,vincent-vivian-liu/redis,AplayER/redis,neomantra/redis,Markgorden/redis,spinlock/redis,Markgorden/redis,narma/redis,seppo0010/rlite-server,gilala/hbjredis,zhiliaoniu/redis,harrisonfeng/redis,gilala/hredis,aim-for-better/redis,fengshao0907/redis,wangyikai/redis,Aliceljm1/redis,hornen/redis,badboy/redis,shining-yang/redis,rogerlz/redis,tellapart/redis,vincent-vivian-liu/redis,linfangrong/redis,xujunhai1991/redis,vincent-vivian-liu/redis,Soledad89/redis,huyuezheng/redis,jingjidejuren/redis,itamarhaber/redis,pedigree/redis,pedigree/redis,abhiklodh/redis,jbochi/parallel_redis,pcarrier/redis,ctripcorp/redis,jasonkying/redis,thomasdarimont/redis,devaos/redis,zczhuohuo/redis,mumingv/redis,xujunhai1991/redis,clamoriniere1A/redis,thomasdarimont/redis,hornen/redis,MOON-CLJ/redis,zhcy/redis,neomantra/redis,cloudrain21/redis,CodeJuan/redis,harrisonfeng/redis,yuhc/redis-benchmark-enhanced,HeartSaVioR/redis,h0x91b/redis,ofirluzon/redis,hgl888/redis,wenxueliu/redis_comment,MasahikoSawada/redis,antirez/redis,neomantra/redis,jbochi/redis,gilala/bjredis,seandsky/redis,ytjiang/redis,fengshao0907/redis,YongMan/redis,seppo0010/redis,iandyh/redis,hgl888/redis,janekmi/redis,clamoriniere1A/redis,SyntaxStacks/redis,xlzhan/redis,alenslan/redis,allengaller/redis,brg-liuwei/redis,HeartSaVioR/redis,yuhc/redis-benchmark-enhanced,hedisdb/hedis,janekmi/redis,honestme/redis,mgk/redis,antirez/redis,xujunhai1991/redis,a-pavlov/redis,mingyaaaa/redis,saisai/redis,mgk/redis,RepmujNetsik/redis,LongXQ/redis,davidradunz/redis,itugs/redis,nnog/redis,Wangyao14cyy/redis,huyuezheng/redis,saisai/redis,valdsJohn/redis,Soledad89/redis,charsyam/redis,zguangyu/redis,soveran/redis,iandyh/redis,izhoujie/redis,takeshineshiro/redis,mcanthony/redis,ouyangkongtong/redis,flashbuckets/redis,wangyikai/redis,jbochi/redis,dreamquster/redis,pcarrier/redis,yossigo/redis,valdsJohn/redis,ErikDubbelboer/redis,z-fork/redis,badboy/redis,shining-yang/redis,Soledad89/redis,ErikDubbelboer/redis,SummonY/redis,sunheehnus/redis,arijitvt/redis,a-pavlov/redis,rogerchina/redis,tanghaodong25/redis,Aaron1992/redis,francischan714/redis,wangyikai/redis,xuguruogu/redis,Soledad89/redis,riyan8250/redis,atreeyang/redis,huyuezheng/redis,tellapart/redis,SummonY/redis,brg-liuwei/redis,francischan714/redis,roth1002/redis,h0x91b/redis,timothyohare/3rdPartySrc-redis,j0hnma/szredis,pcarrier/redis,valdsJohn/redis,holstvoogd/redis,clamoriniere1A/redis,jingjidejuren/redis,yuhc/redis-benchmark-enhanced,OmarQunsul/graph-redis,JoeWoo/redis,twskipper/redis,cnbin/redis,dreamquster/redis,twskipper/redis,neomantra/redis,duanx/redis,PKRoma/redis,rouzier/redis,j0hnma/hszredis,YongMan/redis,kensou97/redis,guker/redis,pkdevbox/redis,jackyan/redis,gilala/bjredis,elkingtonmcb/redis,honestme/redis,CodeJuan/redis,ipmobiletech/redis,dreamquster/redis,ytjiang/redis,programmecat/redis,MOON-CLJ/redis,YuanZhewei/redis,xlzhan/redis,PKRoma/redis,GrimDerp/redis,tjschuck/redis,duanx/redis,cnbin/redis,ituncle/redis,thomasdarimont/redis,soloestoy/redis,soloestoy/redis,xuguruogu/redis,SummonY/redis,linfangrong/redis,janekmi/redis,hawkchch/redis,soveran/redis,colstrom/redis,Sciumo/redis,ouyangkongtong/redis,healerkx/redis,nuxeh/redis,thomasdarimont/redis,dayuoba/redis,jasonkying/redis,MasahikoSawada/redis,elkingtonmcb/redis,RepmujNetsik/redis,YongMan/redis,arijitvt/redis,seppo0010/rlite-server,ton31337/redis,hornen/redis,gaoxianglong/redis,oranagra/redis,itugs/redis,jingjidejuren/redis,devaos/redis,PradheepShrinivasan/redis,blackmady/redis,Sciumo/redis,iandyh/redis,hedisdb/hedis,j0hnma/szredis,neomantra/redis,StevenTsai/redis,zguangyu/redis,citusdata/redis,LongXQ/redis,riyan8250/redis,GitHubMota/redis,itamarhaber/redis,SyntaxStacks/redis,StevenTsai/redis,saisai/redis,gilala/redis,Wangyao14cyy/redis,z-fork/redis,190235047/redis,zhcy/redis,SyntaxStacks/redis,mattsta/redis,soloestoy/redis,itamarhaber/redis,ton31337/redis,AplayER/redis,wujf/redis,weizijun/redis,ncopa/redis,brg-liuwei/redis,GitHubMota/redis,blackmady/redis,hedisdb/hedis,netroby/redis,huyuezheng/redis,LongXQ/redis,j0hnma/szredis,badboy/redis,alenslan/redis,abhiklodh/redis,ytjiang/redis,tjschuck/redis,ctripcorp/redis,programmecat/redis,zguangyu/redis,seppo0010/rlite-server,mumingv/redis,mattsta/redis,nnog/redis,xlzhan/redis,rogerchina/redis,shining-yang/redis,flashbuckets/redis,supasate/redis,StevenTsai/redis,PKRoma/redis,PradheepShrinivasan/redis,honestme/redis,kaushik94/redis,4396/redis,zczhuohuo/redis,seandsky/redis,sunheehnus/redis,shreesundara/redis,Aaron1992/redis,rouzier/redis,josiahcarlson/redis,jackyan/redis,JoeWoo/redis,elkingtonmcb/redis,a-pavlov/redis,elkingtonmcb/redis,h0x91b/redis,mengzhejin/RedisStudy,zhcy/redis,wangyikai/redis,holstvoogd/redis,xuguruogu/redis,wprice/redis,colstrom/redis,aim-for-better/redis,antirez/redis,xujunhai1991/redis,190235047/redis,rouzier/redis,hgl888/redis,roth1002/redis,mumingv/redis,HeartSaVioR/redis,aim-for-better/redis,rogerlz/redis,wbailey5/redis,july2993/redis,charsyam/redis,GitHubMota/redis,charsyam/redis,ofirluzon/redis,NBSW/redis,narma/redis,mengzhejin/RedisStudy,AplayER/redis,ncopa/redis,cusspvz/redis,ctripcorp/redis,izhoujie/redis,healerkx/redis,allengaller/redis,pedigree/redis,pkdevbox/redis,shreesundara/redis,hornen/redis,izhoujie/redis,takeshineshiro/redis,blackmady/redis,YuraLukashik/redis,ofirluzon/redis,dayuoba/redis,linfangrong/redis,SummonY/redis,zguangyu/redis,guker/redis,seppo0010/redis,wbailey5/redis,ofirluzon/redis,mingyaaaa/redis,universsky/redis,YongMan/redis,Sciumo/redis,holstvoogd/redis,wbailey5/redis,nnog/redis,h0x91b/redis,4396/redis,jasonkying/redis,allengaller/redis,Aliceljm1/redis,wujf/redis,saisai/redis,shining-yang/redis,taoguan/redis,simplestbest/redis,fengshao0907/redis,pkdevbox/redis,ituncle/redis,ton31337/redis,NBSW/redis,programmecat/redis,supasate/redis,ouyangkongtong/redis,mengyou0304/redis,AALEKH/redis,modulexcite/redis,modulexcite/redis,gilala/hredis,soveran/redis,narma/redis,dayuoba/redis,clamoriniere1A/redis,riyan8250/redis,kaushik94/redis,j0hnma/szredis,kensou97/redis,MasahikoSawada/redis,YuanZhewei/redis,sunheehnus/redis,modulexcite/redis,harrisonfeng/redis,roth1002/redis,jasonkying/redis,xuguruogu/redis,antirez/redis,zhiliaoniu/redis,wujf/redis,oranagra/redis,taoguan/redis,netroby/redis,ErikDubbelboer/redis,supasate/redis,duanx/redis,kmiku7/redis,csuhawk/redis,mcanthony/redis,GrimDerp/redis,AALEKH/redis,OmarQunsul/graph-redis,ituncle/redis,tjschuck/redis,pcarrier/redis,csuhawk/redis,francischan714/redis,abhiklodh/redis,tellapart/redis,colstrom/redis,AALEKH/redis,qiyang0221/redis,j0hnma/hszredis,ipmobiletech/redis,takeshineshiro/redis,tellapart/redis,PradheepShrinivasan/redis,JoeWoo/redis,badboy/redis,timothyohare/3rdPartySrc-redis,YuraLukashik/redis,vincent-vivian-liu/redis,cusspvz/redis,ncopa/redis,josiahcarlson/redis,mverrilli/redis,charsyam/redis,jackyan/redis,wenxueliu/redis_comment,HeartSaVioR/redis,jackyan/redis,nuxeh/redis