PG: set/clear CREATING in Primary state entry/exit

PG: set/clear CREATING in Primary state entry/exit

Previously, we did not actually set it when we got a pg creation message from
the mon.  It would actually get set on the first start_peering_interval after
that point.  If we don't get that far, but do send a stat update to the mon, we
can end up with 11197.  Instead, let's just set it and clear it upon entry into
and exit from the Primary state.

Fixes: 11197
Signed-off-by: Samuel Just <sjust@redhat.com>
(cherry picked from commit ddf0292250dfb1040d3cad96fa2cf886fd65933c)