🌱 Devstack: Make boot volume optional on openstack

[lentzi90]

What this PR does / why we need it:

This makes it possible to choose if the devstack should be created with or without volumes when running on openstack. It also bumps the default image name to ubuntu-2404-lts to match the other resource types.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

1. Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squashed commits
• if necessary:
  • includes documentation
  • adds unit tests

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[EmilienM]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: EmilienM

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[EmilienM]

@lentzi90 I'll propose the backports. Note that 0.9 backport should be cherry picked into #2306 or wait for it to be merged and then run the bot to backport it.

/cherry-pick release-0.11 release-0.10
0.9 will come later as I said

[k8s-infra-cherrypick-robot]

@EmilienM: new pull request created: #2317

In response to this:

@lentzi90 I'll propose the backports. Note that 0.9 backport should be cherry picked into #2306 or wait for it to be merged and then run the bot to backport it.

/cherry-pick release-0.11 release-0.10
0.9 will come later as I said

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