engine: Adjust Un/LabelNetworkCommand to use commandBase.runInternalAction

UnlabelNetworkCommand and LabelNetworkCommand call UpdateNetworkCommand
internally. For unknown reason they used getBackend().runAction(..) for
this purpose.
Since the call to UpdateNetworkCommand is internal runInternalAction(..)
should be called.
Due to the last changes to CommandBase- commandBase.runInternalAction(..)
should be used.

Change-Id: Ibbe6c0e74129c2ae25d540331a93225181ae41c8
Bug-Url: https://bugzilla.redhat.com/1123636
Signed-off-by: Alona Kaplan <alkaplan@redhat.com>
(cherry picked from commit e71e719e0f8e90b30fb0f7c57ce7de4b07cb963d)