gbproxy: Fix TC_fc_bvc() with more than one SGSN

The altstep was missing the "repeat" at the end, causing it to abort
early and reporting a test failure which actually didn't exist.

Change-Id: I0ec9aa06fa9ec25b2047c1e795e28eeefd6bc7d2

gbproxy/GBProxy_Tests.ttcn

@@ -2430,6 +2430,7 @@ runs on GlobalTest_CT {
 		if (ispresent(tx_reply)) {
 			G_SGSN[sgsn_idx].send(tx_reply);
 		}
+		repeat;
 	}
 }
 /* Send FC-BVC from simulated PCU; expect each SGSN to receive it; expect PCU to receive ACK */