Overlay-related parameters are currently hardcoded in Ansible roles and
scripts (e.g., neutron), regardless of whether overlay networking is
enabled. Allow disabling overlay networking entirely.
Change-Id: I459bd59792ce37725d60725ad5cf5e7e268d18da
Signed-off-by: Arina Triandafilidi <atriandafilidi@mirantis.com>