reload: address warning for preparing tasks

[oliver-sanders]

Address warning for preparing tasks post-reload.

We think after a reload preparing tasks may, or may not, be active with pre-reload settings as the job file may, or may not, have been written. Needs a little investigation and a LOG.warning worded as appropriate.

See #4984 (comment)

Pull requests welcome!

[MetRonnie]

I have looked into this and cannot tell for sure whether a job file would have been written at the point of doing a reload. So having a different warning for preparing tasks saying they "may" be active with pre-reload settings seems sensible.

Possibly we could look at

... be specific by flagging if the job file was written yet, or not.

at a later milestone?

[oliver-sanders]

Sounds good.

I think the mid/long term solution here is probably to flush through preparing tasks before performing the reload for safety.

[MetRonnie]

Closing as partially addressed by #5109, with the long term part being superseded by #5107