etcdmain: remove "listen-metrics-urls" manual parsing
etcdmain: remove "listen-metrics-urls" manual parsing

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

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