Only modify grub configuration if update-grub command is present

[jrosser]

Change description

Only update the grub config on debian based hosts which have the update-grub command available.

#1483 broke the pull-azure-sigs tests and this is a fix for hosts which boot without grub.

Additional context

Boot information from a "confidential" type azure instance suggests it is EFI boot directly to the kernel.

adminuser@instance-0-vm:/boot/grub$ efibootmgr -v
BootCurrent: 0001
Timeout: 0 seconds
BootOrder: 0004,0001,0000
Boot0000* EFI Network	AcpiEx(VMBus,,)/VenHw(9b17e5a2-0891-42dd-b653-80b5c22809ba,635161f83edfc546913ff2d2f965ed0e273a0d001d340d003a27341d000d3a27)/MAC(000000000000,0)/IPv4(0.0.0.00.0.0.0,0,0)
Boot0001* EFI SCSI Device	AcpiEx(VMBus,,)/VenHw(9b17e5a2-0891-42dd-b653-80b5c22809ba,d96361baa104294db60572e2ffb1dc7f1a78b3f8821e1848a1c363d806ec15bb)/SCSI(0,0)
Boot0002* EFI SCSI Device	AcpiEx(VMBus,,)/VenHw(9b17e5a2-0891-42dd-b653-80b5c22809ba,d96361baa104294db60572e2ffb1dc7f1a78b3f8821e1848a1c363d806ec15bb)/SCSI(0,1)
Boot0003* EFI SCSI Device	AcpiEx(VMBus,,)/VenHw(9b17e5a2-0891-42dd-b653-80b5c22809ba,d96361baa104294db60572e2ffb1dc7f1a78b3f8821e1848a1c363d806ec15bb)/SCSI(0,2)
Boot0004* Ubuntu with kernel 6.5.0-1022-azure	HD(15,GPT,f1e55731-4690-417c-801d-ce49fb512839,0x2800,0x200000)/File(\EFI\ubuntu\shimx64.efi)\.k.e.r.n.e.l...e.f.i.-.6...5...0.-.1.0.2.2.-.a.z.u.r.e. .

There are no grub packages or utilities installed on this instance at all, even though there is a /boot/grub/grub.cfg present.

[k8s-ci-robot]

Hi @jrosser. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[AverageMarcus]

I'm curious, does the _ prefix mean anything special here? I've not seen this anywhere else in the codebase I don't think.

[jrosser]

@AverageMarcus it's a convention that i've come across in other projects to signify an internal variable rather than one which is intended to be exposed outside of a role

[AverageMarcus]

/ok-to-test

[AverageMarcus]

/lgtm

/assign @jsturtevant

[jrosser]

/test pull-azure-sigs

[mboersma]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mboersma

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