Fix some golint errors for packages in pkg/kubectl

- Fix some golint errors for `pkg/kubectl`
- Fix a golint error for `pkg/kubectl/apps`
- Fix all golint errors for `pkg/kubectl/cmd`
- Fix some golint errors for `pkg/kubectl/generate/versioned`
- Fix a golint error for `pkg/kubectl/generate`
- Fix some golint errors for `pkg/kubectl/metricsutil`
- Fix all golint errors for `pkg/kubectl/util`
- Fix all golint errors for `pkg/kubectl/util/slice`

pkg/kubectl/generate/generate.go

@@ -102,7 +102,7 @@ func AnnotateFlags(cmd *cobra.Command, generators map[string]Generator) {
 	}
 }
 
-//  EnsureFlagsValid ensures that no invalid flags are being used against a
+// EnsureFlagsValid ensures that no invalid flags are being used against a
 func EnsureFlagsValid(cmd *cobra.Command, generators map[string]Generator, generatorInUse string) error {
 	AnnotateFlags(cmd, generators)