Fix use of clearDelegatesAndCancel
Fix use of clearDelegatesAndCancel

One can notice occasional mismatches in numbers of -addConnection and
connection ends. So to the user, it seems that Vienna never finishes
its work.
Fix found after reading ASIHTTPRequest documentation.
barijaona/vienna-rss,ViennaRSS/vienna-rss,lapcat/vienna-rss,josh64x2/vienna-rss,josh64x2/vienna-rss,Eitot/vienna-rss,ViennaRSS/vienna-rss,josh64x2/vienna-rss,lapcat/vienna-rss,ViennaRSS/vienna-rss,Eitot/vienna-rss,lapcat/vienna-rss,barijaona/vienna-rss,barijaona/vienna-rss,Eitot/vienna-rss,barijaona/vienna-rss,ViennaRSS/vienna-rss,ViennaRSS/vienna-rss,josh64x2/vienna-rss,josh64x2/vienna-rss,barijaona/vienna-rss,Eitot/vienna-rss,lapcat/vienna-rss