CI: Crush rule verification test fails

# Issue report
In MicroCeph Multi Node tests, one of the checks performed is to verify that MicroCeph uses the correct `microceph_rule_host`. Sometimes this check is performed while the crush rule transition has not completely taken place. (see REF)

[REF](https://github.com/canonical/microceph/actions/runs/10350208384/job/28646409576)

## What version of MicroCeph are you using ?
latest/edge

## What are the steps to reproduce this issue ?
CI test

## What happens (observed behaviour) ?
Crush rule is not set to `2`

## What were you expecting to happen ?
Correct crush rule to be configured and the test to pass.

## Relevant logs, error output, etc.
NA, please see REF above in description.

## Additional comments.
NA

Start with the MicroCeph Multi Node test that checks the microceph_rule_host value, then compare its timing with the referenced GitHub Actions run. Trace the crush rule transition and determine how the test observes completion. Done means the check reliably waits for the correct rule value and the CI test passes.

Written by the indexing model from the issue text.