setting hostname of machines using cloud-init

[ykakarap]

What this PR does / why we need it:
This PR make the appropriate changes to cloud-init to set the hostname properly of the machine created.

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 #
This fixes the hostname isse faced on Nimbus VMs.

Special notes for your reviewer:

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

Release note:

[k8s-ci-robot]

Hi @ykakarap. Thanks for your PR.

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[ykakarap]

/cc @figo
/cc @akutz

[figo]

/ok-to-test

[akutz]

/hold

We will likely close this and focus on fixing it in CAPI since this data will be out of our control as we're moving to v1alpha2 on master. That discussion was time boxed and passed last Friday. Therefore these changes need to occur in the new bootstrap controller.

[akutz]

/hold cancel
/lgtm

[frapposelli]

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: frapposelli, ykakarap

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