Update several dependencies in go mod (#2860)

This fix updates several direct dependencies (grpc, aws, protobuf) in go mod,
and removed duplicates with `go mod tidy`

Note: tracing related dependencies are not touched, as
DataDog/tracing dependencies still give trouble.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

go.mod

@@ -3,11 +3,11 @@ module github.com/coredns/coredns
 go 1.12
 
 require (
-	cloud.google.com/go v0.28.0 // indirect
+	cloud.google.com/go v0.39.0 // indirect
 	github.com/DataDog/dd-trace-go v0.6.1 // indirect
 	github.com/Shopify/sarama v1.21.0 // indirect
 	github.com/apache/thrift v0.12.0 // indirect
-	github.com/aws/aws-sdk-go v1.14.17
+	github.com/aws/aws-sdk-go v1.19.41
 	github.com/coreos/bbolt v1.3.2 // indirect
 	github.com/coreos/etcd v3.3.11+incompatible
 	github.com/coreos/go-semver v0.2.0 // indirect
@@ -17,11 +17,10 @@ require (
 	github.com/dnstap/golang-dnstap v0.0.0-20170829151710-2cf77a2b5e11
 	github.com/evanphx/json-patch v4.1.0+incompatible // indirect
 	github.com/farsightsec/golang-framestream v0.0.0-20181102145529-8a0cb8ba8710
-	github.com/go-ini/ini v1.42.0 // indirect
 	github.com/gogo/protobuf v1.2.1 // indirect
 	github.com/golang/groupcache v0.0.0-20190129154638-5b532d6fd5ef // indirect
 	github.com/golang/protobuf v1.3.1
-	github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c // indirect
+	github.com/google/btree v1.0.0 // indirect
 	github.com/google/gofuzz v0.0.0-20170612174753-24818f796faf // indirect
 	github.com/googleapis/gnostic v0.2.0 // indirect
 	github.com/gophercloud/gophercloud v0.0.0-20190307220656-fe1ba5ce12dd // indirect
@@ -31,7 +30,6 @@ require (
 	github.com/grpc-ecosystem/grpc-opentracing v0.0.0-20180507213350-8e809c8a8645
 	github.com/hashicorp/golang-lru v0.5.1 // indirect
 	github.com/imdario/mergo v0.3.7 // indirect
-	github.com/jmespath/go-jmespath v0.0.0-20180206201540-c2b33e8439af // indirect
 	github.com/jonboulle/clockwork v0.1.0 // indirect
 	github.com/json-iterator/go v1.1.5 // indirect
 	github.com/konsorten/go-windows-terminal-sequences v1.0.2 // indirect
@@ -49,7 +47,6 @@ require (
 	github.com/prometheus/common v0.4.1
 	github.com/prometheus/procfs v0.0.0-20190523193104-a7aeb8df3389 // indirect
 	github.com/sirupsen/logrus v1.4.2 // indirect
-	github.com/smartystreets/goconvey v0.0.0-20190306220146-200a235640ff // indirect
 	github.com/soheilhy/cmux v0.1.4 // indirect
 	github.com/spf13/pflag v1.0.3 // indirect
 	github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5 // indirect
@@ -59,21 +56,22 @@ require (
 	go.uber.org/atomic v1.3.2 // indirect
 	go.uber.org/multierr v1.1.0 // indirect
 	go.uber.org/zap v1.9.1 // indirect
-	golang.org/x/crypto v0.0.0-20190513172903-22d7a77e9e5f // indirect
-	golang.org/x/net v0.0.0-20190522155817-f3200d17e092 // indirect
+	golang.org/x/crypto v0.0.0-20190530122614-20be4c3c3ed5 // indirect
+	golang.org/x/net v0.0.0-20190603091049-60506f45cf65 // indirect
+	golang.org/x/oauth2 v0.0.0-20190523182746-aaccbc9213b0 // indirect
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58 // indirect
-	golang.org/x/sys v0.0.0-20190526052359-791d8a0f4d09
+	golang.org/x/sys v0.0.0-20190602015325-4c4f7f33c9ed
 	golang.org/x/text v0.3.2 // indirect
 	golang.org/x/time v0.0.0-20190308202827-9d24e82272b4 // indirect
-	google.golang.org/appengine v1.2.0 // indirect
-	google.golang.org/grpc v1.19.0
+	google.golang.org/appengine v1.6.0 // indirect
+	google.golang.org/genproto v0.0.0-20190530194941-fb225487d101 // indirect
+	google.golang.org/grpc v1.21.0
 	gopkg.in/DataDog/dd-trace-go.v0 v0.6.1
 	gopkg.in/inf.v0 v0.9.1 // indirect
-	gopkg.in/ini.v1 v1.42.0 // indirect
 	k8s.io/api v0.0.0-20190313235455-40a48860b5ab
 	k8s.io/apimachinery v0.0.0-20190313205120-d7deff9243b1
 	k8s.io/client-go v11.0.0+incompatible
-	k8s.io/klog v0.3.1
+	k8s.io/klog v0.3.2
 	k8s.io/kube-openapi v0.0.0-20190306001800-15615b16d372 // indirect
 	k8s.io/utils v0.0.0-20190529001817-6999998975a7 // indirect
 	sigs.k8s.io/yaml v1.1.0 // indirect