confused blessed scroll of remove curse on itself

confused blessed scroll of remove curse on itself

Noticed when testing the set_bknown patch earlier: something updated
the persistent inventory window while scroll processing was in the
midst of traversing invent and it showed the scroll I'd just read
change from known blessed to bless/curse state not known.  The scroll
should really be removed from inventory because player is told that it
has disappeared, but unlike charging (which does do that so that it is
gone when selecting an item to charge), remove curse isn't auto-IDed
and the code to ask the player to call an unIDed item something only
kicks in when it's still in inventory.  Preventing the scroll in use
from having its bknown flag cleared should be good enough; it won't
have disappeared yet but at least it won't be visibly changing.