etcdserver: delete member directory when discovery fails

When discovery fails, etcd node falls back to proxy. And in order to
start as a proxy, we need to make sure there are conflicting directories:
'member' and 'proxy' directories cannot be existent together. This deletes
'member' directory only when startEtcd fails (#3827).

etcdserver/server.go

@@ -194,7 +194,7 @@ 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) {
+func NewServer(cfg *ServerConfig) (srv *EtcdServer, err error) {
 	st := store.New(StoreClusterPrefix, StoreKeysPrefix)
 	var (
 		w  *wal.WAL
@@ -223,12 +223,21 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 	}
 
 	haveWAL := wal.Exist(cfg.WALDir())
+	if !haveWAL {
+		defer func() {
+			if err != nil {
+				// cleans up member directory if bootstrap fails (including forming or joining a new cluster)
+				os.RemoveAll(cfg.MemberDir())
+			}
+		}()
+	}
 	ss := snap.New(cfg.SnapDir())
 
 	prt, err := rafthttp.NewRoundTripper(cfg.PeerTLSInfo, cfg.peerDialTimeout())
 	if err != nil {
 		return nil, err
 	}
+
 	var remotes []*Member
 	switch {
 	case !haveWAL && !cfg.NewCluster:
@@ -335,7 +344,7 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 	sstats.Initialize()
 	lstats := stats.NewLeaderStats(id.String())
 
-	srv := &EtcdServer{
+	srv = &EtcdServer{
 		cfg:       cfg,
 		snapCount: cfg.SnapCount,
 		errorc:    make(chan error, 1),