etcdserver/api/v3rpc: clean up godoc
etcdserver/api/v3rpc: clean up godoc

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

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