Fix gate for enabling FQDN agent registration

If a new version of the charm is used to install a version of
OpenStack prior to Stein, do not enable the FQDN registration.

Change-Id: I64afa582cdfadafcd249ddfbeec267ba610d166a
Closes-Bug: #1846781

hooks/neutron_ovs_context.py

@@ -620,7 +620,8 @@ class HostIPContext(context.OSContextGenerator):
         # We do want to migrate to using FQDNs so we enable this for new
         # installations.
         db = kv()
-        if (db.get('install_version', 0) >= 1910 and cmp_release >= 'stein' and
+        if (db.get('neutron-ovs-charm-use-fqdn', False) and
+                cmp_release >= 'stein' and
                 host_ip):
             fqdn = socket.getfqdn(host_ip)
             if '.' in fqdn:

hooks/neutron_ovs_hooks.py

@@ -82,9 +82,13 @@ CONFIGS = register_configs()
 def install():
     install_packages()
 
-    db = kv()
-    db.set('install_version', 1910)
-    db.flush()
+    # Start migration to agent registration with FQDNs for newly installed
+    # units with OpenStack release Stein or newer.
+    release = os_release('neutron-common')
+    if CompareOpenStackReleases(release) >= 'stein':
+        db = kv()
+        db.set('neutron-ovs-charm-use-fqdn', True)
+        db.flush()
 
 
 # NOTE(wolsen): Do NOT add restart_on_change decorator without consideration

unit_tests/test_neutron_ovs_context.py

@@ -1001,7 +1001,7 @@ class TestHostIPContext(CharmTestCase):
         _getfqdn.return_value = 'some.hostname'
         ctxt = context.HostIPContext()
         self.assertDictEqual({}, ctxt())
-        _kv.return_value = {'install_version': 1910}
+        _kv.return_value = {'neutron-ovs-charm-use-fqdn': True}
         ctxt = context.HostIPContext()
         self.assertDictEqual({'host': 'some.hostname'}, ctxt())
         _os_release.return_value = 'rocky'

unit_tests/test_neutron_ovs_hooks.py

@@ -71,14 +71,19 @@ class NeutronOVSHooksTests(CharmTestCase):
         hooks.hooks.execute([
             'hooks/{}'.format(hookname)])
 
+    @patch.object(hooks, 'os_release')
     @patch.object(hooks, 'kv')
-    def test_install_hook(self, _kv):
+    def test_install_hook(self, _kv, _os_release):
         fake_dict = MagicMock()
         _kv.return_value = fake_dict
+        _os_release.return_value = 'rocky'
         self._call_hook('install')
         self.install_packages.assert_called_with()
+        _os_release.return_value = 'stein'
+        self._call_hook('install')
         _kv.assert_called_once_with()
-        fake_dict.set.assert_called_once_with('install_version', 1910)
+        fake_dict.set.assert_called_once_with(
+            'neutron-ovs-charm-use-fqdn', True)
 
     @patch('neutron_ovs_hooks.enable_sriov', MagicMock(return_value=False))
     @patch.object(hooks, 'restart_map')