msc/USSD: expect and reply SS/USSD messages over GSUP

As we are about to finish the implementation of GSM TS 09.11,
OsmoMSC will forward all SS/USSD messages over GSUP to HLR,
and will expect responses back from HLR. The SS/USSD payload
processing will be out of scope for OsmoMSC itself.

Let's modify the existing test cases in order to expect and
reply SS/USSD messages over GSUP protocol.

Change-Id: I01de73aced6057328a121577a5a83bc2615fb2d4
1 file changed