modification of the parallel test to allow detector padding

[dkazanc]

Checklist

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have made corresponding changes to the documentation

[yousefmoazzam]

The small data pipeline tests that are failing in CI, running them locally outside of pytest shows that the reason the MPI abort is called is because of incorrect args being passed to a tomobar recon function:

TypeError: RecToolsDIRCuPy.__init__() missing 1 required positional argument: 'DetectorsDimH_pad'

I imagine that this is because the httomo CI is pulling in the latest tomobar version on PyPI which has the breaking changes to the recon method's function signatures, but httomolibgpu hasn't yet gotten a new release that accommodates for those changes, which makes the YAML templates generated (and thus the full pipelines generated from the YAML templates + full pipeline directives) for the tomobar methods be based on the old function signatures.

Waiting for the httomolibgpu PR to get merged (DiamondLightSource/httomolibgpu#220) and a subsequent release of httomolibgpu should fix the failing small data pipeline tests here.