Default value of monkey_patch_modules is broken

The default value of monkey_patch_modules has not kept up with
the move of notifier to openstack.common

Without this change setting 'monkey_patch=True' in nova.conf
will cause runtime errors unless the monkey_patch_modules
is also specified pointing to the correct notifier

Change-Id: Ib22faa7404b09791799338de2edfe0ddcd662d5f
Merge "Default value of monkey_patch_modules is broken"