Add check_mode support to HipChat module

The HipChat module declares to support check_mode,
but the message is sent in any case.

With this, if executed in check mode, the module will exit
before actually sending the message to HipChat.

It will return changed=False, as per the convention
for notifications modules.

notification/hipchat.py

@@ -96,6 +96,11 @@ def send_msg(module, token, room, msg_from, msg, msg_format='text',
 
     url = api + "?auth_token=%s" % (token)
     data = urllib.urlencode(params)
+
+    if module.check_mode:
+        # In check mode, exit before actually sending the message
+        module.exit_json(changed=False)
+
     response, info = fetch_url(module, url, data=data)
     if info['status'] == 200:
         return response.read()