fixing working with test data and a small fix for init code

- set init value for `numsdev` to prevent use of uninitialized value
- stop use of 'workdir' and files from samples
- forcing use of 'opencv_extra' instead
Note: set OPENCV_TEST_DATA_PATH to full path to 'opencv_extra/testdata' (gitolite@code.opencv.org:opencv_extra.git) before running the test!

modules/ocl/src/initialization.cpp

@@ -319,7 +319,7 @@ namespace cv
             char clVersion[256];
             for (unsigned i = 0; i < numPlatforms; ++i)
             {
-                cl_uint numsdev;
+                cl_uint numsdev = 0;
                 cl_int status = clGetDeviceIDs(platforms[i], devicetype, 0, NULL, &numsdev);
                 if(status != CL_DEVICE_NOT_FOUND)
                     openCLVerifyCall(status);