IsoHandler::getPacket(): when keeping tabs of the last cycle, allow for cases where...

IsoHandler::getPacket(): when keeping tabs of the last cycle, allow for cases where the m_Client indicates that handling of the cycle should be deferred.  If this is ignored and m_last_cycle is set regardless, the dropped packet logic will be triggered when the cycle is requested again at some later time because the cycle count - when compared to the stored m_last_cycle - will appear to have gone backwards.  This may go some way toward addressing ticket #379, although at the time of writing this is yet to be confirmed.

git-svn-id: svn+ssh://ffado.org/ffado/trunk@2528 2be59082-3212-0410-8809-b0798e1608f0