Remove duplicate error messages from cli commands

Since we never use the cobras "SilenceErrors" or "SilenceUsage",
a command executed with "cmd.Execute()" will never return an error
without printing it.

The current behavior results in all error messages being printed twice:

Example:

$ kubectl abc
Error: unknown command "abc" for "kubectl"
Run 'kubectl --help' for usage.
unknown command "abc" for "kubectl"

This applies to all cli commands using Cobra. To verify, follow the code
path of the Execute function:

https://github.com/spf13/cobra/blob/c439c4fa0937/command.go#L793
Signed-off-by: Odin Ugedal <odin@ugedal.com>

cmd/cloud-controller-manager/controller-manager.go

@@ -20,7 +20,6 @@ limitations under the License.
 package main
 
 import (
-	"fmt"
 	"math/rand"
 	"os"
 	"time"
@@ -48,7 +47,6 @@ func main() {
 	defer logs.FlushLogs()
 
 	if err := command.Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}
 }

cmd/hyperkube/main.go

@@ -61,7 +61,6 @@ func main() {
 
 	basename := filepath.Base(os.Args[0])
 	if err := commandFor(basename, hyperkubeCommand, allCommandFns).Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
 		os.Exit(1)
 	}
 }

cmd/kube-apiserver/apiserver.go

@@ -19,7 +19,6 @@ limitations under the License.
 package main
 
 import (
-	"fmt"
 	"math/rand"
 	"os"
 	"time"
@@ -43,7 +42,6 @@ func main() {
 	defer logs.FlushLogs()
 
 	if err := command.Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}
 }

cmd/kube-controller-manager/controller-manager.go

@@ -21,7 +21,6 @@ limitations under the License.
 package main
 
 import (
-	"fmt"
 	"math/rand"
 	"os"
 	"time"
@@ -45,7 +44,6 @@ func main() {
 	defer logs.FlushLogs()
 
 	if err := command.Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
 		os.Exit(1)
 	}
 }

cmd/kube-proxy/proxy.go

@@ -18,7 +18,6 @@ package main
 
 import (
 	goflag "flag"
-	"fmt"
 	"math/rand"
 	"os"
 	"time"
@@ -47,7 +46,6 @@ func main() {
 	defer logs.FlushLogs()
 
 	if err := command.Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}
 }

cmd/kube-scheduler/scheduler.go

@@ -17,7 +17,6 @@ limitations under the License.
 package main
 
 import (
-	"fmt"
 	"math/rand"
 	"os"
 	"time"
@@ -45,7 +44,6 @@ func main() {
 	defer logs.FlushLogs()
 
 	if err := command.Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
 		os.Exit(1)
 	}
 }

cmd/kubeadm/kubeadm.go

@@ -17,7 +17,6 @@ limitations under the License.
 package main
 
 import (
-	"fmt"
 	"os"
 
 	"k8s.io/klog"
@@ -27,8 +26,6 @@ import (
 func main() {
 	klog.InitFlags(nil)
 	if err := app.Run(); err != nil {
-		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}
-	os.Exit(0)
 }

cmd/kubectl/kubectl.go

@@ -18,7 +18,6 @@ package main
 
 import (
 	goflag "flag"
-	"fmt"
 	"math/rand"
 	"os"
 	"time"
@@ -48,7 +47,6 @@ func main() {
 	defer logs.FlushLogs()
 
 	if err := command.Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
 		os.Exit(1)
 	}
 }

cmd/kubelet/kubelet.go

@@ -21,7 +21,6 @@ limitations under the License.
 package main
 
 import (
-	"fmt"
 	"math/rand"
 	"os"
 	"time"
@@ -40,7 +39,6 @@ func main() {
 	defer logs.FlushLogs()
 
 	if err := command.Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
 		os.Exit(1)
 	}
 }

cmd/kubemark/hollow-node.go

@@ -116,7 +116,6 @@ func main() {
 	defer logs.FlushLogs()
 
 	if err := command.Execute(); err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
 		os.Exit(1)
 	}
 }