Amended polling system to avoid polling succeeded, failed, or expired tasks

[Scott-Owen-James]

Amended polling system to avoid polling succeeded, failed, or expired tasks, closes #7123

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 if present).
• Tests are included (or explain why tests are not needed).
• Changelog entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[oliver-sanders]

I'm not sure if this change addresses the issue of polling "preparing" tasks?

[Scott-Owen-James]

I'm not sure if this change addresses the issue of polling "preparing" tasks?

This is embarrassing, somehow managed to miss it when I was adding other states to ignore, shouldn't be difficult to rectify!