etcdserver/api/v3rpc: remove duplicate gRPC logger set

Fix

=== RUN   TestEmbedEtcd
==================
WARNING: DATA RACE
Write at 0x000001df86d0 by goroutine 711:
  github.com/coreos/etcd/embed.(*Config).setupLogging.func1()
      /go/src/github.com/coreos/etcd/vendor/google.golang.org/grpc/grpclog/loggerv2.go:68 +0x16c
  sync.(*Once).Do()
      /usr/local/go/src/sync/once.go:44 +0xe1
  github.com/coreos/etcd/embed.(*Config).setupLogging()

in gRPC proxy tests.

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

etcdserver/api/v3rpc/grpc.go

@@ -16,10 +16,7 @@ package v3rpc
 
 import (
 	"crypto/tls"
-	"io/ioutil"
 	"math"
-	"os"
-	"sync"
 
 	"github.com/coreos/etcd/etcdserver"
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
@@ -27,7 +24,6 @@ import (
 	"github.com/grpc-ecosystem/go-grpc-prometheus"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
-	"google.golang.org/grpc/grpclog"
 	"google.golang.org/grpc/health"
 	healthpb "google.golang.org/grpc/health/grpc_health_v1"
 )
@@ -38,9 +34,6 @@ const (
 	maxSendBytes      = math.MaxInt32
 )
 
-// integration tests call this multiple times, which is racey in gRPC side
-var grpclogOnce sync.Once
-
 func Server(s *etcdserver.EtcdServer, tls *tls.Config, gopts ...grpc.ServerOption) *grpc.Server {
 	var opts []grpc.ServerOption
 	opts = append(opts, grpc.CustomCodec(&codec{}))
@@ -71,16 +64,5 @@ func Server(s *etcdserver.EtcdServer, tls *tls.Config, gopts ...grpc.ServerOptio
 	// set zero values for metrics registered for this grpc server
 	grpc_prometheus.Register(grpcServer)
 
-	grpclogOnce.Do(func() {
-		if s.Cfg.Debug {
-			grpc.EnableTracing = true
-			// enable info, warning, error
-			grpclog.SetLoggerV2(grpclog.NewLoggerV2(os.Stderr, os.Stderr, os.Stderr))
-		} else {
-			// only discard info
-			grpclog.SetLoggerV2(grpclog.NewLoggerV2(ioutil.Discard, os.Stderr, os.Stderr))
-		}
-	})
-
 	return grpcServer
 }