After parsing flags check that the command is nsenter

Signed-off-by: Michael Crosby <michael@docker.com>

namespaces/nsenter.c

@@ -117,6 +117,10 @@ void nsenter()
 		}
 	}
 
+    if (strcmp(argv[optind], kNsEnter) != 0) {
+        return;
+    }
+
 	if (init_pid_str == NULL) {
 		print_usage();
 		exit(1);

nsinit/exec.go

@@ -50,7 +50,7 @@ func execAction(context *cli.Context) {
 
 // the process for execing a new process inside an existing container is that we have to exec ourself
 // with the nsenter argument so that the C code can setns an the namespaces that we require.  Then that
-// code path will drop us into the path that we can do the file setup of the namespace and exec the users
+// code path will drop us into the path that we can do the final setup of the namespace and exec the users
 // application.
 func startInExistingContainer(config *libcontainer.Config, state *libcontainer.State, context *cli.Context) (int, error) {
 	var (