Fix config loading when running the watcher-api

This regression was caused when we upgrade the version of olso.
Unfortunately this issue wasn't picked up with the unit tests as
the cmds doesn't have unit tests yet.

Error message: "watcher-api fail with NoSuchOptError: no such option:debug"

This patchset implements unit tests for:

- 'watcher-api' command
- 'watcher-db-manage' command (and sub-command)
- 'watcher-applier' command

Change-Id: I2bea8aee28dec913ebc45f2824bf474f86652642

watcher/tests/conf_fixture.py

@@ -19,7 +19,10 @@ from oslo_config import cfg
 
 from watcher.common import config
 
-cfg.CONF.register_opt(cfg.StrOpt('host', default='localhost', help='host'))
+CONF = cfg.CONF
+CONF.import_opt('host', 'watcher.common.service')
+CONF.import_opt('connection', 'oslo_db.options', group='database')
+CONF.import_opt('sqlite_synchronous', 'oslo_db.options', group='database')
 
 
 class ConfFixture(fixtures.Fixture):