Fix bug with redundadnt unbans.
Fix bug with redundadnt unbans.

frumiousbandersnatch/supybot-code,prashantpawar/supybot-rothbot,buildbot/supybot,raboof/supybot,Ban3/Limnoria,mazaclub/mazabot-core,kblin/supybot-gsoc,haxwithaxe/supybot,Ban3/Limnoria,jeffmahoney/supybot,mazaclub/mazabot-core,ProgVal/Limnoria-test,ProgVal/Limnoria-test