Add config option to disable network isolation

This commit adds a new config option to the auth section,
create_isolated_networks, to disable tenant isolation from attempting
to create an isolated network stack on each created tenant. This is
needed because in certain neutron configurations the extra resource
creations are not need or not allowed.

Change-Id: I0899a43709a0cb2967376e914248d2ad4a37773a
Closes-Bug: #1447829
5 files changed