Add the ability to ensure supported kernel

Ubuntu has [deprecated](https://wiki.ubuntu.com/1204_HWE_EOL) all hardware enablement (HWE) kernels (except those which come from LTS releases) which are basically the kernels for newer releases backported to this release. They are named with suffixes of _lts-quantal_, _lts-raring_, _lts-saucy_ and those kernels were only supported until 14.04.1 is released (Aug 8, 2014). The _lts-trusty_ kernel is supported on Ubuntu 12.04 (Precise) because it is backported from Ubuntu 14.04 (Trusty) which is also a Long-Term Support release.

See also #202 for context - the kernel currently on these machines is the original precise kernel which is still supported, however we are forcing them to lts-trusty for consistency with the rest of our estate.