Changes

hnbgw: Send meaningful RANAP messages in f_tc_ranap_mo_disconnect()

Fix the code to send the messages that were fore sure intended, whre an
MO disconnect is triggered.
This allows attaching more to reality, plus making it easier to follow
up the test in wireshark and in the code.

Change-Id: I9a2bb35d58c6cdda312638103ef5c3c2f5661e62