etcdmain: update "help" page
etcdmain: update "help" page

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

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