add check to NewCmdExec before printing suggestion

checks that the "describe" command and a parent command path exist
before printing suggestion to use the describe command to list
containers in a pod.

pkg/kubectl/cmd/cmd.go

@@ -287,7 +287,7 @@ Find more information at https://github.com/kubernetes/kubernetes.`,
 				NewCmdDescribe(f, out, err),
 				NewCmdLogs(f, out),
 				NewCmdAttach(f, in, out, err),
-				NewCmdExec(cmds.Root().CommandPath(), f, in, out, err),
+				NewCmdExec(f, in, out, err),
 				NewCmdPortForward(f, out, err),
 				NewCmdProxy(f, out),
 			},