With 'no assign-tmsi', regard any TMSI as invalidated at the end of a
Location Updating procedure. Hence, avoid paging by TMSI.
When 'no assign-tmsi' is set, osmo-msc does not actively assign a new
TMSI at the end of the Location Updating. However, it stores any TMSI
identity that the MS sends in a Location Updating Request. So far, this
caused osmo-msc to use the TMSI that the MS had sent in subsequent
Paging, which goes unanswered by the MS.
(After the long standing evil twin problem regarding TMSI MI has been
fixed in recent Ifdabe0b65bffafbf7b8e5cc10e2d225d1ed1cecd, there is no
longer an evil twin risked by clearing out a TMSI.)
Related: SYS#6860 OS#4721
Change-Id: I583682d1a35a70b008d7bb2d89ba7c3109a60b21