etcdmain: Add max-snapshots and max-wals to help
etcdmain: Add max-snapshots and max-wals to help

Based on the configuration doc, seems these two flags are missing
in the help. So add them and the descriptions are from config.go in
the same directory.

Signed-off-by: Yiqiao Pu <e4dd1fd40df92fefeedf5e8ca54f533dc9e761f1@redhat.com>

achanda/etcd,bdarnell/etcd,sebrandon1/etcd,sayden/etcd,handsomesun/etcd,lorneli/etcd,xiang90/etcd,OyTao/etcd_learning,sebrandon1/etcd,glevand/coreos--etcd,hongchaodeng/etcd,purpleidea/etcd,sinsharat/etcd,tguangch/etcd,cchamplin/etcd,jonboulle/etcd,etcd-io/etcd,armstrongli/etcd,tamird/etcd,bluebreezecf/etcd,endocode/etcd,glevand/coreos--etcd,joshix/etcd,vimalk78/etcd,yudai/etcd,oscarrr110/etcd,etcd-io/etcd,plasticbox/etcd,tguangch/etcd,zaphod-concur/etcd,achanda/etcd,dannysauer/etcd,YuleiXiao/etcd,heyitsanthony/etcd,xiang90/etcd,luxas/etcd,linuxcer/etcd,visheshnp/etcd,cchamplin/etcd,oscarrr110/etcd,tamird/etcd,fanminshi/etcd,StorReduce/etcd,li-ang/etcd,raoofm/etcd,siddontang/etcd,glycerine/etcd,gyuho/etcd,CrazyJvm/etcd,fasaxc/etcd,endocode/etcd,yudai/etcd,ktateish/etcd,insequent/etcd,dannysauer/etcd,westhood/etcd,jlamillan/etcd,akauppi/etcd,hongchaodeng/etcd,ajityagaty/etcd,rnaveiras/etcd,bluebreezecf/etcd,shawnps/etcd,siddontang/etcd,dnaeon/etcd,coreos/etcd,YuleiXiao/etcd,bdarnell/etcd,mkumatag/etcd,wantonsolutions/dinv-etcd,rchicoli/etcd,plasticbox/etcd,swingbach/etcd,ravigadde/etcd,qqsun8819/etcd,purpleidea/etcd,armstrongli/etcd,sayden/etcd,whuwxl/etcd,Timer/etcd,sofuture/etcd,ajityagaty/etcd,visheshnp/etcd,li-ang/etcd,nekto0n/etcd,OyTao/etcd_learning,rchicoli/etcd,jlamillan/etcd,Timer/etcd,ravigadde/etcd,a-robinson/etcd,gyuho/etcd,glycerine/etcd,wantonsolutions/dinv-etcd,CrazyJvm/etcd,shawnps/etcd,cockroachdb/etcd,fanminshi/etcd,coreos/etcd,lumjjb/etcd,linuxcer/etcd,mqliang/etcd,mickep76/etcd,sofuture/etcd,dnaeon/etcd,StorReduce/etcd,nekto0n/etcd,swingbach/etcd,akauppi/etcd,lorneli/etcd,mqliang/etcd,cockroachdb/etcd,chipironcin/etcd,jonboulle/etcd,joshix/etcd,vimalk78/etcd,qqsun8819/etcd,luxas/etcd,mickep76/etcd,rnaveiras/etcd,ktateish/etcd,handsomesun/etcd,insequent/etcd,lumjjb/etcd,ajityagaty/etcd,a-robinson/etcd,fasaxc/etcd,mqliang/etcd,sinsharat/etcd,mkumatag/etcd,raoofm/etcd,wantonsolutions/dinv-etcd,whuwxl/etcd,etcd-io/etcd,westhood/etcd,zaphod-concur/etcd,rnaveiras/etcd,fasaxc/etcd,mkumatag/etcd,chipironcin/etcd,heyitsanthony/etcd