Adapt XMLSummaryKernel tests to change output file creation policy

This change is needed to fix a couple of tests when gaudi/Gaudi!1432 (merged) is merged.

gaudi/Gaudi!1432 (merged) changes the output file creation policy such that output files are created even if no events are written to them (before they were created on demand when writing the first event to them). This changes the signature of a couple of tests that exercising specific failure modes.

This MR adapts the tests to the new signature of the failures.