[lchan] Keep track which SAPIs has been established with the BTS

Keep track of which SAPIs have been established either by the
BTS (from the MS) or by us. This can be used by the on-waves
BSC code to figure out if a new request should be made.
diff --git a/openbsc/src/chan_alloc.c b/openbsc/src/chan_alloc.c
index 541c6c3..7464aa9 100644
--- a/openbsc/src/chan_alloc.c
+++ b/openbsc/src/chan_alloc.c
@@ -212,6 +212,9 @@
 		lchan->type = type;
 		lchan->use_count = 0;
 
+		/* clear sapis */
+		memset(lchan->sapis, 0, sizeof(lchan->sapis));
+
 		/* Configure the time and start it so it will be closed */
 		lchan->release_timer.cb = auto_release_channel;
 		lchan->release_timer.data = lchan;