ble_mesh: Friend with unknown appkey [Zephyr]

Ensures that friend messages are enqueued, even if the packet is
received with an appkey is unknown to the friend. Previously, sdu_recv
would return EINVAL if the appkey was unknown, which would prevent the
lower transport layer from adding the packet to the friend queue. This
is irrelevant for the logic in lower transport, and should not be
returned as an error.

components/bt/esp_ble_mesh/mesh_core/transport.c

@@ -837,9 +837,11 @@ static int sdu_recv(struct bt_mesh_net_rx *rx, u32_t seq, u8_t hdr,
         return 0;
     }
 
-    BT_WARN("%s, No matching AppKey", __func__);
+    if (rx->local_match) {
+        BT_WARN("%s, No matching AppKey", __func__);
+    }
     bt_mesh_free_buf(sdu);
-    return -EINVAL;
+    return 0;
 }
 
 static struct seg_tx *seg_tx_lookup(u16_t seq_zero, u8_t obo, u16_t addr)