Use unix.Uname instead of exec'ing uname

[tklauser]

Instead of execing the uname(1) command, use the uname(2) syscall directly by means of the unix.Uname wrapper function to get the kernel release.

[k8s-ci-robot]

Hi @tklauser. Thanks for your PR.

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[neolit123]

i think this is fine, just trying to understand the reason for the change.
/cc @pacoxu

[neolit123]

/ok-to-test

[neolit123]

/lgtm

this code will be included in the next release of the lib.
thanks @tklauser

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: neolit123, tklauser

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