bsc: verify MultiRate Config IE in RSL Chan Activ

The current osmo-bsc refactoring causes an erratic MR Config IE. This patch
ensures that the ttcn3-bsc-tests catch this error.

Add MR Config IE expectations to g_pars, set these in the two tests that expect
an MR Config IE in the Chan Activ message:
BSC_Tests.TC_assignment_codec_amr_{f,h}

All other tests now verify that there is *no* MR Config IE in RSL Chan Activ
messages -- all other tests request no voice or a non-AMR codec for Chan Activ.

Change-Id: Ie841feed9d5e478bab1fea2bb86f300e84799013
2 files changed