cloudinit: Fix disabling cloud-init on first boot

`sudo` throws errors and is not even required to write the `disable`
file. Also add a message to the file that it was created by us

Signed-off-by: Cole Robinson <crobinso@redhat.com>

virtinst/install/cloudinit.py

@@ -95,7 +95,8 @@ def _create_userdata_content(cloudinit_data):
 
     if cloudinit_data.disable:
         content += "runcmd:\n"
-        content += "- [ sudo, touch, /etc/cloud/cloud-init.disabled ]\n"
+        content += ('- echo "Disabled by virt-install" > '
+                    "/etc/cloud/cloud-init.disabled\n")
 
     clean_content = re.sub(r"root:(.*)", 'root:[SCRUBBLED]', content)
     if "VIRTINST_TEST_SUITE_PRINT_CLOUDINIT" in os.environ: