Update etcd and grpc to latest version (#3733)

This PR supersede 3664. With recent etcd changes, we can finally
get around the bump caused by incompatiblity between grpc and etcd.

This fix closes 3664.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

go.mod

@@ -14,8 +14,6 @@ require (
 	github.com/caddyserver/caddy v1.0.5
 	github.com/cenkalti/backoff/v4 v4.0.0
 	github.com/coredns/federation v0.0.0-20190818181423-e032b096babe
-	github.com/coreos/go-systemd v0.0.0-20190212144455-93d5ec2c7f76 // indirect
-	github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f // indirect
 	github.com/dnstap/golang-dnstap v0.0.0-20170829151710-2cf77a2b5e11
 	github.com/farsightsec/golang-framestream v0.0.0-20181102145529-8a0cb8ba8710
 	github.com/golang/groupcache v0.0.0-20190129154638-5b532d6fd5ef // indirect
@@ -35,11 +33,13 @@ require (
 	github.com/prometheus/common v0.9.1
 	github.com/tinylib/msgp v1.1.0 // indirect
 	github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5 // indirect
-	go.etcd.io/etcd v0.5.0-alpha.5.0.20190917205325-a14579fbfb1a
+	go.etcd.io/etcd v0.5.0-alpha.5.0.20200306183522-221f0cc107cb
 	golang.org/x/crypto v0.0.0-20191206172530-e9b2fee46413
-	golang.org/x/sys v0.0.0-20200122134326-e047566fdf82
+	golang.org/x/net v0.0.0-20200301022130-244492dfa37a // indirect
+	golang.org/x/sys v0.0.0-20200302150141-5c8b2ff67527
 	google.golang.org/api v0.15.0
-	google.golang.org/grpc v1.26.0
+	google.golang.org/genproto v0.0.0-20200306153348-d950eab6f860 // indirect
+	google.golang.org/grpc v1.27.1
 	gopkg.in/DataDog/dd-trace-go.v1 v1.22.0
 	k8s.io/api v0.17.3
 	k8s.io/apimachinery v0.17.3