deduplicate kernel_version open-coded parser

[aquini]

The code that parses kernel version from OSRELEASE/UTSRELEASE strings and populates the global kernel table is duplicated across the codebase for no good reason. This commit consolidates all the duplicated parsing code into a single method to remove the unnecessary duplicated code.

[k-hagio]

Closing with f774fe0f59b45596e5165eb008845b3534f650d0, thanks.