the MS Serbian Latin Neutral mess

There are two LangID values mapping to Serbian Latin (without country)
which lead to the UI language selector displaying "sr-Latn" instead of
"Serbian Latin" because conversion picked the other one. Consistently
use LANGUAGE_SERBIAN_LATIN_LSO and don't trap into
LANGUAGE_SERBIAN_LATIN_NEUTRAL (whatever that might be).

Change-Id: I6ae6c2027048c99096b4d9d703a0dc73784b52f1
(cherry picked from commit 4256491ffe48b8be09ec66a003988193e8585584)