Fix coverage test failure: e2e TestIssue6361.

Tested with:
```
(cd tests && COVERDIR='../../c' 'env' 'go' 'test' '-tags=cov' '-timeout' '30m' 'go.etcd.io/etcd/tests/v3/e2e' -run TestIssue6361 -v 2>&1 | tee log.log)
```

tests/e2e/cluster_test.go

@@ -25,6 +25,7 @@ import (
 
 	"go.etcd.io/etcd/server/v3/etcdserver"
 	"go.etcd.io/etcd/tests/v3/integration"
+	"go.uber.org/zap"
 	"go.uber.org/zap/zaptest"
 )
 
@@ -134,6 +135,7 @@ func configStandalone(cfg etcdProcessClusterConfig) *etcdProcessClusterConfig {
 }
 
 type etcdProcessCluster struct {
+	lg    *zap.Logger
 	cfg   *etcdProcessClusterConfig
 	procs []etcdProcess
 }
@@ -182,6 +184,7 @@ func newEtcdProcessCluster(t testing.TB, cfg *etcdProcessClusterConfig) (*etcdPr
 	etcdCfgs := cfg.etcdServerProcessConfigs(t)
 	epc := &etcdProcessCluster{
 		cfg:   cfg,
+		lg:    zaptest.NewLogger(t),
 		procs: make([]etcdProcess, cfg.clusterSize),
 	}
 
@@ -451,6 +454,7 @@ func (epc *etcdProcessCluster) Stop() (err error) {
 }
 
 func (epc *etcdProcessCluster) Close() error {
+	epc.lg.Info("closing test cluster...")
 	err := epc.Stop()
 	for _, p := range epc.procs {
 		// p is nil when newEtcdProcess fails in the middle
@@ -462,6 +466,7 @@ func (epc *etcdProcessCluster) Close() error {
 			err = cerr
 		}
 	}
+	epc.lg.Info("closed test cluster.")
 	return err
 }
 

tests/e2e/ctl_v3_snapshot_test.go

@@ -193,7 +193,6 @@ func TestIssue6361(t *testing.T) {
 	}
 
 	fpath := filepath.Join(t.TempDir(), "test.snapshot")
-	defer os.RemoveAll(fpath)
 
 	t.Log("etcdctl saving snapshot...")
 	if err = spawnWithExpect(append(prefixArgs, "snapshot", "save", fpath), fmt.Sprintf("Snapshot saved at %s", fpath)); err != nil {
@@ -206,7 +205,6 @@ func TestIssue6361(t *testing.T) {
 	}
 
 	newDataDir := filepath.Join(t.TempDir(), "test.data")
-	defer os.RemoveAll(newDataDir)
 
 	t.Log("etcdctl restoring the snapshot...")
 	err = spawnWithExpect([]string{ctlBinPath, "snapshot", "restore", fpath, "--name", epc.procs[0].Config().name, "--initial-cluster", epc.procs[0].Config().initialCluster, "--initial-cluster-token", epc.procs[0].Config().initialToken, "--initial-advertise-peer-urls", epc.procs[0].Config().purl.String(), "--data-dir", newDataDir}, "added member")
@@ -273,4 +271,5 @@ func TestIssue6361(t *testing.T) {
 	if err = nepc.Stop(); err != nil {
 		t.Fatal(err)
 	}
+	t.Log("Test logic done")
 }

tests/e2e/etcd_process.go

@@ -90,23 +90,34 @@ func (ep *etcdServerProcess) Start() error {
 	if ep.proc != nil {
 		panic("already started")
 	}
+	ep.cfg.lg.Info("starting server...", zap.String("name", ep.cfg.name))
 	proc, err := spawnCmdWithLogger(ep.cfg.lg, append([]string{ep.cfg.execPath}, ep.cfg.args...))
 	if err != nil {
 		return err
 	}
 	ep.proc = proc
-	return ep.waitReady()
+	err = ep.waitReady()
+	if err == nil {
+		ep.cfg.lg.Info("started server.", zap.String("name", ep.cfg.name))
+	}
+	return err
 }
 
 func (ep *etcdServerProcess) Restart() error {
+	ep.cfg.lg.Info("restaring server...", zap.String("name", ep.cfg.name))
 	if err := ep.Stop(); err != nil {
 		return err
 	}
 	ep.donec = make(chan struct{})
-	return ep.Start()
+	err := ep.Start()
+	if err == nil {
+		ep.cfg.lg.Info("restared server", zap.String("name", ep.cfg.name))
+	}
+	return err
 }
 
 func (ep *etcdServerProcess) Stop() (err error) {
+	ep.cfg.lg.Info("stoping server...", zap.String("name", ep.cfg.name))
 	if ep == nil || ep.proc == nil {
 		return nil
 	}
@@ -123,13 +134,16 @@ func (ep *etcdServerProcess) Stop() (err error) {
 			return err
 		}
 	}
+	ep.cfg.lg.Info("stopped server.", zap.String("name", ep.cfg.name))
 	return nil
 }
 
 func (ep *etcdServerProcess) Close() error {
+	ep.cfg.lg.Info("closing server...", zap.String("name", ep.cfg.name))
 	if err := ep.Stop(); err != nil {
 		return err
 	}
+	ep.cfg.lg.Info("removing directory", zap.String("data-dir", ep.cfg.dataDirPath))
 	return os.RemoveAll(ep.cfg.dataDirPath)
 }