cylc-rose run twice bug

[wxtim]

This is a small change with no associated Issue:

Cylc was forced to run cylc-rose twice under some circumstances to give uninstalled workflows access to CLI variables. This PR passes CLI variable to Parsec instead.

Partner of cylc/cylc-rose#92 - Both are required for testing.
It replaces #4462 .

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.py and
  conda-environment.yml.
• Already covered by existing tests, these are in the Cylc Rose repo.
• No Change log entry included because this PR makes existing functionality work slighty faster and without a confusing double error message.
• No documentation update required.

[MetRonnie]

Partial review

[MetRonnie]

I am a little confused about how this pairs with cylc/cylc-rose#92 - there doesn't seem to be any changes to the entry points there. Had the change to the entry point(s) already happened in an earlier PR?

[wxtim]

I am a little confused about how this pairs with cylc/cylc-rose#92 - there doesn't seem to be any changes to the entry points there. Had the change to the entry point(s) already happened in an earlier PR?

The functionality this PR uses has existed in Cylc Rose for a long time, but hadn't been used by the code in parsec/fileparse before - it should have been, hence the PR