gbproxy: Fix log messages in timeout situations

Printing an unbound 'rx' variable when nothing was received due to
timeout is somehow not really useful.  Print what we expected to
receive.

Change-Id: Idab8bed06281468164006682aa6b4c2c3e236880

gbproxy/GBProxy_Tests.ttcn

@@ -571,7 +571,7 @@ friend function f_pcu2sgsn(template (value) PDU_BSSGP tx, template (present) PDU
 		mtc.stop;
 		}
 	[] T.timeout {
-		setverdict(fail, "Timeout waiting for BSSGP on SGSN side: ", rx);
+		setverdict(fail, "Timeout waiting for BSSGP on SGSN side: ", exp_rx);
 		mtc.stop;
 		}
 	}
@@ -606,7 +606,7 @@ friend function f_sgsn2pcu(template (value) PDU_BSSGP tx, template (present) PDU
 		mtc.stop;
 		}
 	[] T.timeout {
-		setverdict(fail, "Timeout waiting for BSSGP on PCU side: ", rx);
+		setverdict(fail, "Timeout waiting for BSSGP on PCU side: ", exp_rx);
 		mtc.stop;
 		}
 	}