mgcp_protocol: fix loop that sends dummy RTP packets

The logic in mgcp_keepalive_timer_cb() only sends dummy packets for
endpoints 1-N, leaving out endpoint 0, this is not correct it should
include all endpoints (0-N).

Change-Id: I99a9b572eac26780bc1286a8dd63c4c5652fda4f
diff --git a/src/libosmo-mgcp/mgcp_protocol.c b/src/libosmo-mgcp/mgcp_protocol.c
index 56271e2..29d27d4 100644
--- a/src/libosmo-mgcp/mgcp_protocol.c
+++ b/src/libosmo-mgcp/mgcp_protocol.c
@@ -1494,7 +1494,7 @@
 
 	/* Send walk over all endpoints and send out dummy packets through
 	 * every connection present on each endpoint */
-	for (i = 1; i < trunk->number_endpoints; ++i) {
+	for (i = 0; i < trunk->number_endpoints; ++i) {
 		struct mgcp_endpoint *endp = trunk->endpoints[i];
 		llist_for_each_entry(conn, &endp->conns, entry) {
 			if (conn->type == MGCP_CONN_TYPE_RTP &&