Removed 'watcher_messaging' to use oslo.messaging

The old 'watcher_messaging' section of the Watcher configuration file
has now been replaced by the more standard oslo.configuration one.

DocImpact

Change-Id: Ie027df023e6133f3188e57b42846083f28c282bd

watcher/tests/conf_fixture.py

@@ -34,7 +34,6 @@ class ConfFixture(fixtures.Fixture):
     def setUp(self):
         super(ConfFixture, self).setUp()
 
-        self.conf.set_default('host', 'fake-mini')
         self.conf.set_default('connection', "sqlite://", group='database')
         self.conf.set_default('sqlite_synchronous', False, group='database')
         self.conf.set_default('verbose', True)