Allow networks to be updated

Neutron will allow you to update certain properties of the network after
creation. This change modifies the ansible code to perform an update
call if it detects that any updatable properties have been changed. If
you attempt to change a property that cannot be updated, the module will
fail. This gives you confidence that the ansible configuration matches
the state of the network in OpenStack. If we did not fail in this way,
you might think you have updated the network, but in reality those
changes would be silently ignored. Prior to this change, the only way to
update properties of a network was to delete it and then recreate.

Story: 2010024
Task: 45262
Change-Id: I4af2b50f207f349b58c63e0a4e92816ada0847fd