Clear the update lock for the enabled fileserver backends

        back
            Only clear the update lock for the specified backend(s). The
            default is to clear the lock for all enabled backends

        remote
            If specified, then any remotes which contain the passed string will
            have their lock cleared.

def clear_lock(self, back=None, remote=None):
        '''
        Clear the update lock for the enabled fileserver backends

        back
            Only clear the update lock for the specified backend(s). The
            default is to clear the lock for all enabled backends

        remote
            If specified, then any remotes which contain the passed string will
            have their lock cleared.
        '''
        back = self.backends(back)
        cleared = []
        errors = []
        for fsb in back:
            fstr = '{0}.clear_lock'.format(fsb)
            if fstr in self.servers:
                good, bad = clear_lock(self.servers[fstr],
                                       fsb,
                                       remote=remote)
                cleared.extend(good)
                errors.extend(bad)
        return cleared, errors