Fixing bug which fails to recognise Bs --> K*bar mu mu as b --> dll transition (LHCBGAUSS-1097).
In EvtGen model EvtbTosllVectorAmp Bs --> K*bar mu mu is not properly recognised as b --> dll transition, but rather handled as b --> sll transition. Needs check added to properly recognise this decay.
This should propagate also to other branches.