ctlv3: ensure synced member list before printing env vars on member add
ctlv3: ensure synced member list before printing env vars on member add

In cases of multiple endpoints, it's possible member add would get a its
member list from a member that has not yet recognized the membership
update. Instead, confirm that the member list response is from the
member that acked the member add or from a member that has synced
with the cluster following the member add.

Fixes #7498

jlamillan/etcd,joshix/etcd,fanminshi/etcd,mickep76/etcd,cockroachdb/etcd,sebrandon1/etcd,plasticbox/etcd,li-ang/etcd,tguangch/etcd,lorneli/etcd,handsomesun/etcd,sinsharat/etcd,fanminshi/etcd,yudai/etcd,YuleiXiao/etcd,mickep76/etcd,bdarnell/etcd,ajityagaty/etcd,sinsharat/etcd,joshix/etcd,visheshnp/etcd,mkumatag/etcd,sebrandon1/etcd,li-ang/etcd,lorneli/etcd,dannysauer/etcd,armstrongli/etcd,mqliang/etcd,handsomesun/etcd,a-robinson/etcd,yudai/etcd,rnaveiras/etcd,etcd-io/etcd,whuwxl/etcd,cockroachdb/etcd,akauppi/etcd,etcd-io/etcd,akauppi/etcd,heyitsanthony/etcd,bdarnell/etcd,armstrongli/etcd,mqliang/etcd,coreos/etcd,xiang90/etcd,gyuho/etcd,bluebreezecf/etcd,mqliang/etcd,YuleiXiao/etcd,mkumatag/etcd,ajityagaty/etcd,visheshnp/etcd,etcd-io/etcd,whuwxl/etcd,lumjjb/etcd,jlamillan/etcd,vimalk78/etcd,rnaveiras/etcd,glevand/coreos--etcd,dannysauer/etcd,xiang90/etcd,tguangch/etcd,gyuho/etcd,coreos/etcd,mkumatag/etcd,lumjjb/etcd,glevand/coreos--etcd,a-robinson/etcd,heyitsanthony/etcd,vimalk78/etcd,plasticbox/etcd,rnaveiras/etcd,ajityagaty/etcd,bluebreezecf/etcd