Adding energy_tracer.add_pstate_change in server_on_turn_onoff_hosts

[marcodamico]

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Describe what the pull request does
Adding a missing call of energy_tracer.add_pstate_change in server_on_turn_onoff_hosts.
I am not 100% sure it is necessary, but the old code did it.

This branch already includes #76, so it should be approved after #76 is merged.

Checklist

Branch name.

• Descriptive and short
• Use hyphens to separate words

Branch content.

• Only dedicated to the problem.
• Based on Batsim's official main branch.
• Straightforward. Just a sequence of commits. Does not contain merge commits.
• Test results are not worse than before. How to run Batsim tests?

[bleuse]

Commit 9f1f914 looks like a good catch indeed.
I'll see how we deal with the integration of this commit regardless of the status of #76 or this PR.

[Mommessc]

The second commit has been cherry-picked into the main branch (713313e), thank you!