scripts: fix read failure prompt in release; use https for git clone.
scripts: fix read failure prompt in release; use https for git clone.

etcd-io/etcd,ajityagaty/etcd,rnaveiras/etcd,rnaveiras/etcd,cockroachdb/etcd,rnaveiras/etcd,gyuho/etcd,mqliang/etcd,ajityagaty/etcd,etcd-io/etcd,ajityagaty/etcd,mqliang/etcd,mkumatag/etcd,coreos/etcd,li-ang/etcd,cockroachdb/etcd,dannysauer/etcd,coreos/etcd,etcd-io/etcd,mqliang/etcd,mkumatag/etcd,dannysauer/etcd,gyuho/etcd,mkumatag/etcd,li-ang/etcd