Handle PBS 19.2.1+ job names.

[hjoliver]

These changes close #4539

@dpmatthews - is this simple fix sufficient?

Requirements check-list

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg and conda-environment.yml.
• covered by existing tests (presumbably, covered by PBS test if run using recent PBS versions)?
• Appropriate change log entry included.
• No documentation update required.

[dpmatthews]

I've confirmed this fixes the problem

[datamel]

Code read, branch checked out and I have confirmed the flaky test that was failing passes locally for me. I have re-run the checks and it is now passing.
No change log entry as yet, otherwise looks good to me.

[hjoliver]

Change log updated.