This partially reverts 510b32b7156625b9df737c916b7a7a5c6fb285b9 since it
still necessary to take a reference before calling dbus_watch_handle
since internally it can call watch_info_free as in the following trace:

 Invalid read of size 8
   at 0x121085: watch_func (mainloop.c:105)
   by 0x4C72694: g_main_context_dispatch (gmain.c:2539)
   by 0x4C729C7: g_main_context_iterate.isra.23 (gmain.c:3146)
   by 0x4C72DC1: g_main_loop_run (gmain.c:3340)
   by 0x120541: main (main.c:551)
 Address 0x5bbcd90 is 16 bytes inside a block of size 24 free'd
   at 0x4A079AE: free (vg_replace_malloc.c:427)
   by 0x4C7837E: g_free (gmem.c:252)
   by 0x4F708BF: dbus_watch_set_data (dbus-watch.c:614)
   by 0x4F70938: _dbus_watch_unref (dbus-watch.c:132)
   by 0x4F6E9A7: _dbus_transport_handle_watch (dbus-transport.c:884)
   by 0x4F59AFB: _dbus_connection_handle_watch (dbus-connection.c:1497)
   by 0x4F70AF9: dbus_watch_handle (dbus-watch.c:683)
   by 0x121084: watch_func (mainloop.c:103)
   by 0x4C72694: g_main_context_dispatch (gmain.c:2539)
   by 0x4C729C7: g_main_context_iterate.isra.23 (gmain.c:3146)
   by 0x4C72DC1: g_main_loop_run (gmain.c:3340)
   by 0x120541: main (main.c:551)