blur samples are failing in Linux CI

The `blur` and `blurcpp` samples are failing in Linux CI. I am not sure why. They are passing for me locally, on all of the OpenCL implementations I've tried. So, it is possible that this is a sample issue, though it is more likely that it is an issue with the OpenCL implementation we are testing with in CI.

Start with the Linux CI logs and the `blur` and `blurcpp` samples to identify the failing checks and reproduce the difference from local OpenCL implementations. Done means determining whether the failure is in a sample or the OpenCL implementation used by CI, then making the affected CI checks pass.

Written by the indexing model from the issue text.