handover: Call bsc_handover_clear from gsm0808_clear

The bsc_handover_clear will release an in-progress handover
and free the lchana and the data associated with this handover
diff --git a/openbsc/src/bsc_api.c b/openbsc/src/bsc_api.c
index 9c1d090..856dc61 100644
--- a/openbsc/src/bsc_api.c
+++ b/openbsc/src/bsc_api.c
@@ -28,6 +28,7 @@
 #include <openbsc/signal.h>
 #include <openbsc/abis_rsl.h>
 #include <openbsc/chan_alloc.h>
+#include <openbsc/handover.h>
 
 #include <osmocore/talloc.h>
 
@@ -115,6 +116,8 @@
 {
 	struct gsm_lchan *lchan;
 
+	bsc_clear_handover(conn);
+
 	lchan = conn->lchan;
 	subscr_con_free(conn);
 	lchan_release(lchan, 1, 0);