Saves the list of installed repo XML settings files.

def _save_installed(self):
        """Saves the list of installed repo XML settings files."""
        import json
        from utility import json_serial, get_json
        #This is a little tricky because the data file doesn't just have a list
        #of installed servers. It also manages the script's database that tracks
        #the user's interactions with it.
        fulldata = get_json(self.instpath, {})
        fulldata["installed"] = self.installed
        with open(self.instpath, 'w') as f:
            json.dump(fulldata, f, default=json_serial)