ignore PORT messages after dht destroyed (fix #601)
ignore PORT messages after dht destroyed (fix #601)

jamesliu96/webtorrent,rom1504/webtorrent,jamesliu96/webtorrent,feross/webtorrent,webtorrent/webtorrent,webtorrent/webtorrent,yciabaud/webtorrent,feross/webtorrent,joshterrill/webtorrent,yciabaud/webtorrent,joshterrill/webtorrent,arestov/webtorrent