ttcn3-msc-test/osmo-msc.cfg: disable encryption for UTRAN
The Iu/UMTS specific test cases in ttcn3-msc-test expect no encryption in Security Mode Command by default (only integrity), while osmo-msc would permit both UEA1 and UEA2 unless configured explicitly. This causes the related test cases to fail.
A similar change was merged to osmo-ttcn3-hacks, updating the osmo-msc.cfg in there, however the actual configuration file that is used to execute test cases on Jenkins was not updated.