BSC_Tests: add testcases to verify S15-S0 handling

The handling of the AMR rate configuration bits S15-S0 is currently only
superficially checked. Lets add more some more elaborated testcases to
check through varios different situations. Also make sure that the
resulting mr configuration IE is verified

Change-Id: Ica323deb9836deea72982e093c9cb31deb5a216b
Related: SYS#4470
3 files changed