etcdserver: delete member directory when NewServer errors

This is for etcd-io#3827.
This removes member directory with defer statement. And it removes only when
etcdserver.NewServer returns error.

etcdserver/server.go

@@ -195,6 +195,16 @@ type EtcdServer struct {
 // NewServer creates a new EtcdServer from the supplied configuration. The
 // configuration is considered static for the lifetime of the EtcdServer.
 func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
+	isSuccess := false
+	defer func() {
+		if !isSuccess {
+			// It removes member directory when NewServer returns error.
+			// This prevents conflicts with 'proxy' directory when
+			// the node falls back to proxy.
+			os.RemoveAll(cfg.MemberDir())
+		}
+	}()
+
 	st := store.New(StoreClusterPrefix, StoreKeysPrefix)
 	var (
 		w  *wal.WAL
@@ -394,6 +404,7 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 	}
 	srv.r.transport = tr
 
+	isSuccess = true
 	return srv, nil
 }