Update rabbit driver config options

The stein version of python-oslo.messaging (9.0.0+) has removed
the following config options from the [oslo_messaging_rabbit]
section:

rabbit_host, rabbit_port, rabbit_hosts, rabbit_userid,
rabbit_password, rabbit_virtual_host rabbit_max_retries, and
rabbit_durable_queues.

The above change requires a sync from charm-helpers.

Additionally the transport_url directive has been moved to the
[DEFAULT] section.

These have been deprecated since Ocata, therefore this change
will be provided to pre-Stein templates in order to drop
deprecation warnings.

See release notes at:
https://docs.openstack.org/releasenotes/oslo.messaging/index.html

test_300_neutron_config is also removed in this change as amulet
tests no longer need to confirm config file settings.

Change-Id: I3c22b6ca1992b3c20ed83afc430545999096d370
Closes-Bug: #1817672

hooks/charmhelpers/contrib/openstack/context.py

@@ -29,6 +29,7 @@ from charmhelpers.fetch import (
     filter_installed_packages,
 )
 from charmhelpers.core.hookenv import (
+    NoNetworkBinding,
     config,
     is_relation_made,
     local_unit,
@@ -868,7 +869,7 @@ class ApacheSSLContext(OSContextGenerator):
                     addr = network_get_primary_address(
                         ADDRESS_MAP[net_type]['binding']
                     )
-                except NotImplementedError:
+                except (NotImplementedError, NoNetworkBinding):
                     addr = fallback
 
             endpoint = resolve_address(net_type)