Server sometimes takes over 1s to capture image

Image capture should be quick ~0.1s, sometimes it takes over 1s causing an error. This has been causing crashes (See #293 (closed), these were silent due to an error handling issues)

We can fix the crashes by increasing the timeout in the image customiser (see raspberry-pi-os-image-customiser#4 (closed)), this will close #293 (closed). But not fix this underlying problem.

Next steps

Systematically record capture timings during some scans and see if we can pin down what is causing the issue.