etcdmain: warn when listening on HTTP if TLS is set

If the user sets TLS info, this implies that he wants to listen on TLS.
If etcd finds that urls to listen is still HTTP schema, it prints out
warning to notify user about possible wrong setting.

etcdmain/etcd.go

@@ -146,6 +146,9 @@ func startEtcd(cfg *config) (<-chan struct{}, error) {
 	}
 	plns := make([]net.Listener, 0)
 	for _, u := range cfg.lpurls {
+		if u.Scheme == "http" && !cfg.peerTLSInfo.Empty() {
+			plog.Warningf("The scheme of peer url %s is http while peer key/cert files are presented. Ignored peer key/cert files.", u.String())
+		}
 		var l net.Listener
 		l, err = transport.NewTimeoutListener(u.Host, u.Scheme, cfg.peerTLSInfo, rafthttp.ConnReadTimeout, rafthttp.ConnWriteTimeout)
 		if err != nil {
@@ -168,6 +171,9 @@ func startEtcd(cfg *config) (<-chan struct{}, error) {
 	}
 	clns := make([]net.Listener, 0)
 	for _, u := range cfg.lcurls {
+		if u.Scheme == "http" && !cfg.clientTLSInfo.Empty() {
+			plog.Warningf("The scheme of client url %s is http while client key/cert files are presented. Ignored client key/cert files.", u.String())
+		}
 		var l net.Listener
 		l, err = transport.NewKeepAliveListener(u.Host, u.Scheme, cfg.clientTLSInfo)
 		if err != nil {