'Updates config.check_tcp or check_ignore, depending on attr.'

def _host_pattern_on(self, attr):

    assert (not hasattr(self, ('_ignore_%s_backup' % attr)))
    backup = []
    for proxy in self.chain:
        old_matcher = getattr(proxy.tmaster.server.config, ('check_%s' % attr))
        backup.append(old_matcher)
        setattr(proxy.tmaster.server.config, ('check_%s' % attr), HostMatcher(([('.+:%s' % self.server.port)] + old_matcher.patterns)))
    setattr(self, ('_ignore_%s_backup' % attr), backup)
