fedora-atomic: add in override for vagrant sync location

Go ahead and update the fedora-atomic.conf so that when it gets
branched it will have the override already in there.

Signed-off-by: Dusty Mabe <dusty@dustymabe.com>

fedora-atomic.conf

@@ -252,7 +252,10 @@ image_build = {
                     ],
                     'install_tree_from': 'Cloud',
                     'subvariant': 'Atomic'
-                     }
+                     },
+            'factory-parameters': {
+                    'vagrant_sync_directory': '/home/vagrant/sync',
+            }
         }
         ],
 }