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: I4fee89baa954736ae8298b63667297dd57d8ec4f

gbproxy/GBProxy_Tests.ttcn

@@ -765,7 +765,7 @@ friend function f_global_pcu2sgsn(template (value) PDU_BSSGP tx, template (prese
 		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;
 		}
 	}
@@ -788,7 +788,7 @@ friend function f_global_sgsn2pcu(template (value) PDU_BSSGP tx, template (prese
 		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;
 		}
 	}