fix B13006 - Unchanging-poly self-genocide

fix B13006 - Unchanging-poly self-genocide

     <Someone> reported that killing yourself by picking your current
monster class as the target of a blessed scroll of genocide while
polymorphed and wearing an amulet of unchanging would result in
"killed by genocide" rather than "killed by a scroll of genocide".
That wasn't the only problem here; it also ended the game right away,
before genociding the rest of the class of monsters; that could affect
the contents of a resulting bones level.

     Also, the 3.3.0 race/class split resulted in getting the message
"you feel dead inside" twice if you were a human or elf character who
genocides '@' while polymorphed into some non-@ form.