gbproxy: Use "force-unconifgured" als on BSS-side NSEs

Any NSE should be unconfigured at start up of the test case in order
to avoid any state leakage from previous test executions into the
newly-started test case.

Change-Id: I1dd491d5bce17b4602f1e26b42df003f1627714a

gbproxy/GBProxy_Tests.ttcn

@@ -375,6 +375,7 @@ function f_init() runs on test_CT {
 	}
 	f_sleep(4.0);
 	for (i := 0; i < lengthof(mp_nsconfig_pcu); i := i+1) {
+		f_vty_transceive(GBPVTY, "nsvc nsei " & int2str(g_pcu[i].cfg.nsei) & " force-unconfigured");
 		f_init_gb_pcu(g_pcu[i], "GbProxy_Test", i);
 	}