Check a keyid for membership in a autosign directory.

def check_autosign_dir(self, keyid):
        '''
        Check a keyid for membership in a autosign directory.
        '''
        autosign_dir = os.path.join(self.opts['pki_dir'], 'minions_autosign')

        # cleanup expired files
        expire_minutes = self.opts.get('autosign_timeout', 120)
        if expire_minutes > 0:
            min_time = time.time() - (60 * int(expire_minutes))
            for root, dirs, filenames in salt.utils.path.os_walk(autosign_dir):
                for f in filenames:
                    stub_file = os.path.join(autosign_dir, f)
                    mtime = os.path.getmtime(stub_file)
                    if mtime < min_time:
                        log.warning('Autosign keyid expired %s', stub_file)
                        os.remove(stub_file)

        stub_file = os.path.join(autosign_dir, keyid)
        if not os.path.exists(stub_file):
            return False
        os.remove(stub_file)
        return True