msc: Expect CommonID from MSC by default

As of osmo-msc Change-Id I2552736477663adb250c55728093500e8ae83ebb,
osmo-msc is always sending BSSMAP CommonID to the BSC.  Let's adjust our
test expectation, while allowing the user to start the tests with
BSC_ConnectionHandler.mp_expect_common_id := false
to get the existing behavior (expect no bSSMAP CommonId) can be
restored, e.g. for testing 'latest'.

Change-Id: I4976d9bb1f07c8ab4ffa02848414f8ddd1bdfd3f
Related: OS#2969
diff --git a/msc/MSC_Tests.ttcn b/msc/MSC_Tests.ttcn
index 5497c2d..d668616 100644
--- a/msc/MSC_Tests.ttcn
+++ b/msc/MSC_Tests.ttcn
@@ -807,6 +807,7 @@
 
 	/* Send BSSAP_Conn_Req with COMPL L3 INFO to MSC */
 	f_cl3_or_initial_ue(l3_lu);
+	f_expect_common_id();
 
 	/* Send Early Classmark, just for the fun of it */
 	BSSAP.send(ts_BSSMAP_ClassmarkUpd(g_pars.cm2, g_pars.cm3));
@@ -926,6 +927,7 @@
 	BSSAP.receive(tr_PDU_DTAP_MT(tr_ML3_MT_MM_ID_Req(CM_ID_TYPE_IMSI)));
 	BSSAP.send(ts_PDU_DTAP_MO(ts_ML3_MO_MM_ID_Rsp_IMSI(overlong_imsi))); /* test for OS#2864 */
 	BSSAP.send(ts_PDU_DTAP_MO(ts_ML3_MO_MM_ID_Rsp_IMSI(g_pars.imsi)));
+	f_expect_common_id();
 
 	/* Expect MSC to do UpdateLocation to HLR; respond to it */
 	GSUP.receive(tr_GSUP_UL_REQ(g_pars.imsi));
@@ -3972,6 +3974,7 @@
 		mtc.stop;
 		}
 	}
+	f_expect_common_id();
 
 	/* Expect LU reject from MSC. */
 	alt {
@@ -4008,6 +4011,7 @@
 	/* Send BSSAP_Conn_Req with COMPL L3 INFO to MSC */
 	var PDU_ML3_MS_NW l3_lu := f_build_lu_imsi(g_pars.imsi)
 	f_cl3_or_initial_ue(l3_lu);
+	f_expect_common_id();
 
 	/* Expect LU reject from MSC. */
 	alt {
@@ -4066,6 +4070,7 @@
 		mtc.stop;
 		}
 	}
+	f_expect_common_id();
 
 	/* TODO: Verify MSC is using the best cipher available! How? */