Ansible launcher: add option to keep jobdir

To aid in debugging.

Change-Id: Ice4478fd7b6d4121ed9f1c7c9bce1dcc57699a3a
diff --git a/zuul/cmd/launcher.py b/zuul/cmd/launcher.py
index 86266b3..c9516f8 100644
--- a/zuul/cmd/launcher.py
+++ b/zuul/cmd/launcher.py
@@ -46,6 +46,9 @@
         parser.add_argument('--version', dest='version', action='version',
                             version=self._get_version(),
                             help='show zuul version')
+        parser.add_argument('--keep-jobdir', dest='keep_jobdir',
+                            action='store_true',
+                            help='keep local jobdirs after run completes')
         self.args = parser.parse_args()
 
     def reconfigure_handler(self, signum, frame):
@@ -73,7 +76,8 @@
         self.log = logging.getLogger("zuul.Launcher")
 
         LaunchServer = zuul.launcher.ansiblelaunchserver.LaunchServer
-        self.launcher = LaunchServer(self.config)
+        self.launcher = LaunchServer(self.config,
+                                     keep_jobdir=self.args.keep_jobdir)
         self.launcher.start()
 
         signal.signal(signal.SIGHUP, self.reconfigure_handler)