Fix availability zone API tests

Currently, if you run the availability zone API tests when not using
the no-op drivers, the API tests will fail as they had hard-coded
availability zone names that do not exist.
Since creating availability zones requires reconfiguration of the nova
host deployments, it is not practical to create nova availability zones
for these tests.

This patch adds tempest configuration settings for the required
availability zones, and if not configured will skip the tests that
require the availability zones be present.

Change-Id: I53d5d33ae9a181b79e1d971d56452eeee5dd7759
diff --git a/octavia_tempest_plugin/config.py b/octavia_tempest_plugin/config.py
index 8573d89..fc04c33 100644
--- a/octavia_tempest_plugin/config.py
+++ b/octavia_tempest_plugin/config.py
@@ -195,6 +195,12 @@
     cfg.StrOpt('availability_zone',
                default=None,
                help='Availability zone to use for creating servers.'),
+    cfg.StrOpt('availability_zone2',
+               default=None,
+               help='A second availability zone to use for creating servers.'),
+    cfg.StrOpt('availability_zone3',
+               default=None,
+               help='A third availability zone to use for creating servers.'),
     cfg.BoolOpt('test_reuse_connection', default=True,
                 help='Reuse TCP connections while testing LB with '
                      'HTTP members (keep-alive).'),