Gear: bind to a specified address

Along with gear's I884e0ddcaac9c7de35b913dc967a47ee854d0a8a, this is
needed to make sure that the local Gear server listens on a correct
interface -- it should be the same one as we use for contacting it later
on.

FIXME: add a dependency on new enough Gear once it's merged & released.

Change-Id: Ia5a0d098f57dcdb3a730c43ab56e55f61127afe8

zuul/cmd/server.py

@@ -119,6 +119,7 @@ class Server(zuul.cmd.ZuulApp):
             statsd_host = os.environ.get('STATSD_HOST')
             statsd_port = int(os.environ.get('STATSD_PORT', 8125))
             gear.Server(4730,
+                        host=self.config.get('gearman', 'server'),
                         statsd_host=statsd_host,
                         statsd_port=statsd_port,
                         statsd_prefix='zuul.geard')