MacGui: removed a old check on the scan count from the era when the MacGui used a single libhb instance to encode and scan, and fixed a bug it was hiding: spurious calls to hb_get_state outside the updateUI loop were masking the HB_STATE_WORKDONE and HB_STATE_SCANDONE states, replaced them with hb_get_state2.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6274 b64f7644-9d1e-0410-96f1-a4d463321fa5