[nrf fromtree] Bluetooth: Mesh: Release previously reserved slot before reserving again

If the previous upload was in-band and it didn't complete, the slot will
stay reserved. By design we release slot not at the end of the upload
phase, but at the start of a new upload phase.

This fixes DFU/SR/FD/BV-13-C.

Signed-off-by: Pavel Vasilyev <[email protected]>
(cherry picked from commit d1c2ca2)

Author: PavelVPV

subsys/bluetooth/mesh/dfd_srv.c

@@ -607,6 +607,13 @@ static int handle_upload_start_oob(struct bt_mesh_model *mod, struct bt_mesh_msg
 		return 0;
 	}
 
+	/* This will be a no-op if the slot state isn't RESERVED, which is
+	 * what we want.
+	 */
+	if (srv->upload.slot) {
+		bt_mesh_dfu_slot_release(srv->upload.slot);
+	}
+
 	srv->upload.is_oob = true;
 	srv->upload.slot = slot;
 	memcpy(srv->upload.oob.uri, uri, uri_len);