HLR_Tests.ttcn: introduce TC_mo_sss_reject

As at the moment, OsmoHLR doesn't support "structured" SS, such
requests are being rejected. This test case aims to verify that.

Change-Id: I147b919d0242b3b44e39a4587bf1b4660fa58bd2
Related: OS#3651
diff --git a/hlr/expected-results.xml b/hlr/expected-results.xml
index 5431b78..8a1ed26 100644
--- a/hlr/expected-results.xml
+++ b/hlr/expected-results.xml
@@ -17,4 +17,5 @@
   <testcase classname='HLR_Tests' name='TC_mo_ussd_euse' time='MASKED'/>
   <testcase classname='HLR_Tests' name='TC_mo_ussd_euse_continue' time='MASKED'/>
   <testcase classname='HLR_Tests' name='TC_mo_ussd_euse_defaultroute' time='MASKED'/>
+  <testcase classname='HLR_Tests' name='TC_mo_sss_reject' time='MASKED'/>
 </testsuite>