This patch simplifies the container_updater unit test code by
refactoring the creation of the continer_updater into a helper method.
This method by default will use a default configuration. However
this configuration can be changed by passing in a dictionary of
configuration elements to update, for example:
self._get_container_updater({'mount_check': 'true'})
Change-Id: Ide211d559bf9381c520a04cd90d278d9b2beae50