store: fix race in watcher_hub
store: fix race in watcher_hub

Get the lock before modifing the global objects in the hub.

chai2010/etcd,mwitkow/etcd,wantonsolutions/dinv-etcd,yichengq/etcd,crandles/etcd,tempbottle/etcd,westhood/etcd,hongbinz/etcd,swingbach/etcd,ajityagaty/etcd,qiaochao911/etcd,mqliang/etcd,armstrongli/etcd,snailwalker/etcd,etcd-io/etcd,wfxiang08/etcd,njucslqq/etcd,spacejam/etcd,Yhgenomics/etcd,yudai/etcd,glycerine/etcd,nieanan/etcd,chipironcin/etcd,es-chow/etcd,fgbreel/etcd,mickep76/etcd,gtank/etcd,giantswarm/etcd,chenbaihu/etcd,insequent/etcd,barakmich/etcd,westhood/etcd,bakins/etcd,endocode/etcd,gosharplite/etcd,nieanan/etcd,shakefu/etcd,mike-lerch/etcd,crandles/etcd,iamqizhao/etcd,betawaffle/etcd,iamqizhao/etcd,YuleiXiao/etcd,tamird/etcd,handsomesun/etcd,lorneli/etcd,chai2010-playground/etcd,siddontang/etcd,honeyqa/etcd,YuleiXiao/etcd,devfreesg/etcd,devfreesg/etcd,princeqjzh/etcd,mqliang/etcd,olark/etcd,insionng/etcd,openedbox/etcd,jefby/etcd,dnaeon/etcd,bspline/etcd,njucslqq/etcd,improbable-io/etcd,coreos/etcd,tangkun75/etcd,wowsoso/etcd,tguangch/etcd,purpleidea/etcd,mwitkow-io/etcd,li-ang/etcd,vimalk78/etcd,plasticbox/etcd,wantonsolutions/dinv-etcd,SivagnanamCiena/etcd,yyljlyy/etcd,jravetch/etcd,chenbaihu/etcd,ajityagaty/etcd,StorReduce/etcd,ktateish/etcd,gae123/etcd,tguangch/etcd,fasaxc/etcd,jchauncey/etcd,pauldallen/etcd,freeloop1114/etcd,chai2010/etcd,arthurcolle/etcd,csuideal/etcd,jlamillan/etcd,endocode/etcd,snailwalker/etcd,luxas/etcd,mitake/etcd,handsomesun/etcd,bluebreezecf/etcd,gyuho/etcd,mwitkow/etcd,tamird/etcd,mgoelzer/etcd-fork2,achanda/etcd,msanterre/etcd,visheshnp/etcd,buaazp/etcd,sebschrader/etcd,dannysauer/etcd,ktateish/etcd,shawnps/etcd,joshix/etcd,lzbgt/etcd,combk8s/etcd,xychu/etcd,mkumatag/etcd,ajityagaty/etcd,dalanlan/etcd,rnaveiras/etcd,Eagle-X/etcd,jeremyeder/etcd,swingbach/etcd,cchamplin/etcd,pengzj/etcd,rnaveiras/etcd,olark/etcd,gtank/etcd,ravigadde/etcd,Winslett/etcd,shafreeck/etcd,jmptrader/etcd,betawaffle/etcd,hroyrh/etcd,imzhulei/etcd,youxidev/etcd,vimalk78/etcd,svdata/etcd,fasaxc/etcd,joshix/etcd,jlamillan/etcd,sebrandon1/etcd,honeyqa/etcd,etcd-io/etcd,li-ang/etcd,cockroachdb/etcd,sinsharat/etcd,bdarnell/etcd,freeloop1114/etcd,jefby/etcd,ecnahc515/etcd,sebschrader/etcd,achanda/etcd,xychu/etcd,Timer/etcd,gosharplite/etcd,lzbgt/etcd,insionng/etcd,glensc/etcd,sebrandon1/etcd,xebitstudios/etcd,xebitstudios/etcd,jravetch/etcd,asim/etcd,mitake/etcd,raoofm/etcd,kingland/etcd,bdarnell/etcd,youxidev/etcd,njharman/etcd,xdlinear/etcd,wfxiang08/etcd,wowsoso/etcd,princeqjzh/etcd,msanterre/etcd,cchamplin/etcd,svdata/etcd,dannysauer/etcd,polvi/etcd,kingland/etcd,Yhgenomics/etcd,OyTao/etcd_learning,gyuho/etcd,sofuture/etcd,bakins/etcd,ylong/etcd,lorneli/etcd,wantonsolutions/dinv-etcd,yyljlyy/etcd,xiang90/etcd,cognusion/etcd,nkhare/etcd,jonboulle/etcd,beni55/etcd,jmptrader/etcd,Timer/etcd,polvi/etcd,delkyd/etcd,buaazp/etcd,rnaveiras/etcd,chai2010-playground/etcd,zaphod-concur/etcd,mkumatag/etcd,imzhulei/etcd,shafreeck/etcd,spacejam/etcd,justintung/etcd,glevand/coreos--etcd,nkhare/etcd,fgbreel/etcd,barakmich/etcd,HideoYamauchi/etcd,luxas/etcd,xdlinear/etcd,rchicoli/etcd,yudai/etcd,whuwxl/etcd,linuxcer/etcd,cockroachdb/etcd,qqsun8819/etcd,a-robinson/etcd,etcd-io/etcd,ylong/etcd,junxu/etcd,rchicoli/etcd,lumjjb/etcd,pengzj/etcd,HideoYamauchi/etcd,ravigadde/etcd,kkaneda/etcd,es-chow/etcd,akauppi/etcd,justintung/etcd,pauldallen/etcd,steveeJ/etcd,mike-lerch/etcd,insequent/etcd,offscale/etcd,glevand/coreos--etcd,gouyang/etcd,fanminshi/etcd,bluebreezecf/etcd,xiang90/etcd,yifan-gu/etcd,hzy001/etcd,gouyang/etcd,Eagle-X/etcd,offscale/etcd,bspline/etcd,delkyd/etcd,ecnahc515/etcd,elimisteve/etcd,sinsharat/etcd,hzy001/etcd,xueshanf/etcd,purpleidea/etcd,TheHippo/etcd,jonboulle/etcd,akauppi/etcd,qiaochao911/etcd,njharman/etcd,shawnps/etcd,fasaxc/etcd,whuwxl/etcd,QuantiumTechnology/etcd,tempbottle/etcd,cognusion/etcd,coreos/etcd,mwitkow-io/etcd,TheHippo/etcd,siddontang/etcd,combk8s/etcd,mischief/etcd,gityf/etcd,axingblog/etcd,mickep76/etcd,a-robinson/etcd,csuideal/etcd,plasticbox/etcd,junxu/etcd,lumjjb/etcd,steveeJ/etcd,zaphod-concur/etcd,linuxcer/etcd,xueshanf/etcd,shakefu/etcd,hpcloud/etcd,giantswarm/etcd,SivagnanamCiena/etcd,beni55/etcd,axingblog/etcd,robszumski/etcd,fanminshi/etcd,qqsun8819/etcd,elimisteve/etcd,CrazyJvm/etcd,mgoelzer/etcd-fork2,hpcloud/etcd,nekto0n/etcd,openedbox/etcd,mkumatag/etcd,yifan-gu/etcd,glycerine/etcd,improbable-io/etcd,gae123/etcd,hongchaodeng/etcd,dalanlan/etcd,hroyrh/etcd,visheshnp/etcd,sayden/etcd,robszumski/etcd,jchauncey/etcd,onlyjob/etcd,arthurcolle/etcd,oscarrr110/etcd,glensc/etcd,oscarrr110/etcd,jeremyeder/etcd,onlyjob/etcd,CrazyJvm/etcd,armstrongli/etcd,asim/etcd,mischief/etcd,kkaneda/etcd,gityf/etcd,hongchaodeng/etcd,nekto0n/etcd,raoofm/etcd,yichengq/etcd,QuantiumTechnology/etcd,heyitsanthony/etcd,hongbinz/etcd,sofuture/etcd,dnaeon/etcd,StorReduce/etcd,OyTao/etcd_learning,mqliang/etcd,tangkun75/etcd,Winslett/etcd,chipironcin/etcd,sayden/etcd,heyitsanthony/etcd