silence error messages about HANDOVER_END not permitted

The MSC_A_EV_HANDOVER_END exists as parent term event for the msc_ho_fsm, but
it is not actually required as functional event, since all cleanup is handled
in msc_ho_fsm_cleanup().

That's why I never bothered to add the event to msc_a_fsm, but of course that
means we get an error message after each (successful and unsuccessful)
handover, that the MSC_A_EV_HANDOVER_END is not permitted.

Allow the event and ignore it to silence the error message.
Explain in a comment.

Change-Id: Ie8dc0c0a631b7da43111f329562007766a21b134
1 file changed