Ensure strong ref to obj before calling persistent_to_deleted, others

Ensure strong ref to obj before calling persistent_to_deleted, others

Add checks in spots where state.obj() might be late-GC'ed before
we get a chance to call the event.   There may be more cases
of these which we should address as they come up.  The Session
should always be maintaining strong refs to objects that have
pending operations left on them, so for these cases we need
to ensure that ref remains long enough for the event to be called.

Change-Id: I1a7c7bc57130acc11f54ad55924af2e36ac75101
Fixes: #3808