daemon: Clean up switchKernel a bit && vendor: Bump coreos/rpm-ostree-client-go

[cgwalters]

daemon: Clean up switchKernel a bit

De-duplicate calls to canonicalizeKernelType to make the
logic easier to read. Also add a few comments.

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vendor: Bump coreos/rpm-ostree-client-go

In prep for usage in MCD.

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[openshift-ci]

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[openshift-ci]

@cgwalters: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/e2e-hypershift	2b8b903	link	false	/test e2e-hypershift
ci/prow/okd-scos-e2e-aws-ovn	2b8b903	link	false	/test okd-scos-e2e-aws-ovn
ci/prow/e2e-alibabacloud-ovn	2b8b903	link	false	/test e2e-alibabacloud-ovn
ci/prow/okd-scos-e2e-gcp-ovn-upgrade	2b8b903	link	false	/test okd-scos-e2e-gcp-ovn-upgrade

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[cgwalters]

OK this one passed CI, so in theory we could merge it indepenently of #3580 but we might as well just target that one.
(But it's good to have the CI signal from passing here)