This patch adds a check to determine if the 'segments' service plugin is
enabled. The segment-host mapping db table should only be saved and
updated to the db table if the users configure the 'segments' service
plugin in the config file. The data should be available only in a routed
network resource situation.
Conflicts:
neutron/tests/unit/extensions/test_segment.py
NOTE(s10): conflict is due to If6792d121e7b8e1ab4c7a548982a42e69023da2b
not being in Queens
Change-Id: I65a42aa2129bef696906a18d82575461dc02ba21
Closes-Bug: #1799328
(cherry picked from commit 06ba6a1ace)
(cherry picked from commit 7f8c446d5f)