Recover camera capture and release mmap buffers before reconnecting

tests/stubs/opencv2/videoio.hpp

@@ -0,0 +1,19 @@
+#pragma once
+// Camera timeout tests exercise live capture only. Stub the unused replay API
+// so the use-can Camera can be tested without OpenCV or a video decoder.
+#include <stdexcept>
+#include <string>
+namespace cv {
+constexpr int CAP_PROP_FRAME_WIDTH=3,CAP_PROP_FRAME_HEIGHT=4;
+struct Mat {
+    int cols{},rows{};
+    unsigned char const* ptr(int)const {throw std::logic_error("Video replay is outside this test");}
+};
+class VideoCapture {
+public:
+    bool isOpened()const{return false;}
+    bool open(std::string const&){throw std::logic_error("Video replay is outside this test");}
+    double get(int)const {throw std::logic_error("Video replay is outside this test");}
+    bool read(Mat&){throw std::logic_error("Video replay is outside this test");}
+};
+}