avoid use-after-free: on MGW endpoint dealloc, also forget it in conn->ho.*

With the FORGET_MGW_ENDPOINT event, the MGW endpoint FSM notifies the gscon
that it has deallocated and that hence the gscon should forget all references
to it (to avoid a use-after-free).

Also do this for the endpoint FSM and endpoint ci pointers in the conn->ho.*
sub struct.

I saw a use-after-free after a Handover Failure message tears down the lchan
and MGW endpoint before triggering the handover_fsm.c cleanup code, which also
tries to clean up an endpoint CI if it was created for the failed Handover.

Change-Id: I6702ccd0df44bea5eb8b26d471d7903c24e6e30b
1 file changed