Ansible launcher: some ansible fixes

These were causing ansible errors:

* required and default are mutually exclusize
* don't return rc from the zuul_log module
* the initial timeout, if not set, will arrive as the string 'None'

Change-Id: I0129c01d5fb365b81812553eeaf6b3d91acf8f55

zuul/ansible/library/zuul_log.py

@@ -41,13 +41,13 @@ def log(msg):
 def main():
     module = AnsibleModule(
         argument_spec=dict(
-            msg=dict(required=True, default=''),
+            msg=dict(required=True),
         )
     )
 
     p = module.params
-    ret = log(p['msg'])
-    module.exit_json(changed=True, rc=ret)
+    log(p['msg'])
+    module.exit_json(changed=True)
 
 from ansible.module_utils.basic import *  # noqa
 

zuul/ansible/plugins/callback_plugins/timeout.py

@@ -49,7 +49,7 @@ class CallbackModule(CallbackBase):
             facts = dict(elapsed_time=self._elapsed_time)
 
             overall_timeout = manager.extra_vars.get('timeout')
-            if overall_timeout is not None:
+            if str(overall_timeout) != 'None':
                 timeout = int(overall_timeout) - int(self._elapsed_time)
                 facts['timeout'] = timeout