wait for subscriber conn in TC_cipher_complete_with_invalid_cipher

Ensure that tests running after TC_cipher_complete_with_invalid_cipher
won't see a left-over subscriber connection at the MSC.

Change-Id: If26ee688f77cdb80557e9695b8e3920fa2ce6706
Related: OS#2872
diff --git a/msc/MSC_Tests.ttcn b/msc/MSC_Tests.ttcn
index 1b37329..d121b63 100644
--- a/msc/MSC_Tests.ttcn
+++ b/msc/MSC_Tests.ttcn
@@ -2815,6 +2815,7 @@
 		mtc.stop;
 		}
 	}
+	f_expect_clear();
 }
 
 testcase TC_cipher_complete_with_invalid_cipher() runs on MTC_CT {