Add test for MS mode and (M)CS settings

Right now set_mode() on GprsMs behaves in pretty counter-intuitive way:
* it's possible to set current DL MCS higher than max value
* EGPRS and EGPRS_GMSK have the same max DL MCS
* setting EGPRS* mode drops current/max MCS values to unknown

Let's capture this in a unit-test before attempting any further
modifications.

Change-Id: Ibf917f4b49d927a21cbd467775806fa6ea06a6a6
diff --git a/tests/ms/MsTest.err b/tests/ms/MsTest.err
index a2e4a0c..735c4fe 100644
--- a/tests/ms/MsTest.err
+++ b/tests/ms/MsTest.err
@@ -56,3 +56,6 @@
 Destroying MS object, TLLI = 0xffeeddbb
 Creating MS object, TLLI = 0xffeeddbb
 Attaching TBF to MS object, TLLI = 0xffeeddbb, TBF = TBF(TFI=0 TLLI=0xffeeddbb DIR=DL STATE=NULL)
+Creating MS object, TLLI = 0xdeadbeef
+Creating MS object, TLLI = 0xdeadbef0
+Attaching TBF to MS object, TLLI = 0xdeadbef0, TBF = TBF(TFI=0 TLLI=0xdeadbef0 DIR=DL STATE=NULL)