vty: Classify the application that we run and provide different options

The VTY interface is used for three different application and not
every option will make sense for every app. In the long run we will
split the vty interface but for now we just qualify the application.
diff --git a/src/main_stp.c b/src/main_stp.c
index 36e04d6..328eabe 100644
--- a/src/main_stp.c
+++ b/src/main_stp.c
@@ -184,6 +184,7 @@
 	struct mtp_m2ua_link *lnk;
 	INIT_LLIST_HEAD(&bsc.sccp_connections);
 
+	bsc.app = APP_STP;
 	bsc.dpc = 1;
 	bsc.opc = 0;
 	bsc.sccp_opc = -1;