Avoid double call to set ofono's online property

On initialization a double call to set-soft was being done for the ofono device. This caused bugs LP #1392397 and #1379807.
There ought to be something better to do than trying to delay stuff with signals during a removal. If that can't be done, then consider passing a custom struct that would be freed in the callback rather than anything else, from which to retrieve the object pointer and these, maybe a gboolean disposed.