CHANGELOG-3.4: highlight etcd server "raft.ErrProposalDropped" return
CHANGELOG-3.4: highlight etcd server "raft.ErrProposalDropped" return

Signed-off-by: Gyuho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

coreos/etcd,li-ang/etcd,etcd-io/etcd,mkumatag/etcd,rnaveiras/etcd,mkumatag/etcd,fanminshi/etcd,dannysauer/etcd,gyuho/etcd,rnaveiras/etcd,ajityagaty/etcd,joshix/etcd,xiang90/etcd,bdarnell/etcd,etcd-io/etcd,bdarnell/etcd,gyuho/etcd,sebrandon1/etcd,ajityagaty/etcd,sinsharat/etcd,sebrandon1/etcd,vimalk78/etcd,coreos/etcd,lorneli/etcd,dannysauer/etcd,xiang90/etcd,mqliang/etcd,joshix/etcd,cockroachdb/etcd,lorneli/etcd,mqliang/etcd,rnaveiras/etcd,mqliang/etcd,ajityagaty/etcd,etcd-io/etcd,glevand/coreos--etcd,li-ang/etcd,glevand/coreos--etcd,mkumatag/etcd,fanminshi/etcd,cockroachdb/etcd,sinsharat/etcd,vimalk78/etcd