ble_mesh: Skip local messages in rx

Local messages are already enqueued for the LPN in the tx path, and
don't have to be added again in the rx path.

components/bt/esp_ble_mesh/mesh_core/friend.c

@@ -1310,6 +1310,14 @@ static void friend_lpn_enqueue_rx(struct bt_mesh_friend *frnd,
     struct friend_pdu_info info;
     struct net_buf *buf;
 
+    /* Because of network loopback, tx packets will also be passed into
+     * this rx function. These packets have already been added to the
+     * queue, and should be ignored.
+     */
+    if (bt_mesh_elem_find(rx->ctx.addr)) {
+        return;
+    }
+
     BT_DBG("LPN 0x%04x queue_size %u", frnd->lpn, frnd->queue_size);
 
     if (type == BLE_MESH_FRIEND_PDU_SINGLE && seq_auth) {