[nrf fromlist] tests: bluetooth: tester: Fix BLOB server model pointer

PTS uses BLOB server model instantiated by DFD server for MBT tests as
it is the first BLOB server model in the device composition data. DFU
server, which also has BLOB server model, is instantiated after DFD
server.

Upstream PR: zephyrproject-rtos/zephyr#63904
Signed-off-by: Pavel Vasilyev <[email protected]>
(cherry picked from commit 83bc101)

Author: PavelVPV

tests/bluetooth/tester/src/btp_mesh.c

@@ -4468,10 +4468,10 @@ static uint8_t blob_srv_recv(const void *cmd, uint16_t cmd_len,
 	struct model_data *model_bound;
 	int err;
 
-#if defined(CONFIG_BT_MESH_DFU_SRV)
-	struct bt_mesh_blob_srv *srv = &dfu_srv.blob;
-#elif defined(CONFIG_BT_MESH_DFD_SRV)
+#if defined(CONFIG_BT_MESH_DFD_SRV)
 	struct bt_mesh_blob_srv *srv = &dfd_srv.upload.blob;
+#elif defined(CONFIG_BT_MESH_DFU_SRV)
+	struct bt_mesh_blob_srv *srv = &dfu_srv.blob;
 #endif
 
 	model_bound = lookup_model_bound(BT_MESH_MODEL_ID_BLOB_SRV);