GabbleServerTLSManager: stop making assumptions about how Wocky implements its async callback
GabbleServerTLSManager: stop making assumptions about how Wocky implements its async callback

In principle, we're not meant to assume anything about @result - even
that it's a GSimpleAsyncResult.

(This broke when Wocky changed its source tags from _finish to the
more conventional _async.)

mlundblad/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,jku/telepathy-gabble