Allow pinning kernel versions to work around hardware / driver issues

Allow pinning kernel versions to work around hardware / driver issues

Sometimes hardware issues or driver issues are fixed or broken in
specific kernel versions, so it's handy to be able to pin the
version to a known-working one while the problem is sorted out or
a proper fix is found.

This does this by ensuring that the particular kernel version package
is installed and that the grub configuration boots that as the default.

For context, see https://github.com/openstreetmap/operations/issues/45