bsc: A BTS excluded from the RF lock should be allowed to make a connection

When introducing the exclude for the BTS lock the RF stayed up but
all connections were immediately released. Optionally pass the BTS
as second parameter and check the exclude bit.

Tested-with: rf-lock-exclude/RFLockExcludeTest.st
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_grace.c b/openbsc/src/osmo-bsc/osmo_bsc_grace.c
index 3f73b50..ad0a37e 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_grace.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_grace.c
@@ -24,10 +24,12 @@
 #include <openbsc/gsm_04_80.h>
 #include <openbsc/signal.h>
 
-int bsc_grace_allow_new_connection(struct gsm_network *network)
+int bsc_grace_allow_new_connection(struct gsm_network *network, struct gsm_bts *bts)
 {
 	if (!network->bsc_data->rf_ctrl)
 		return 1;
+	if (bts && bts->excl_from_rf_lock)
+		return 1;
 	return network->bsc_data->rf_ctrl->policy == S_RF_ON;
 }