[SRU] Set the default IO scheduler to CFQ in Kubuntu Trusty

[Rohan Garg]

> A consistent kernel and performance expectations across Ubuntu is also
> worthwhile. I don't want someone screw up database/VM/etc. workloads
> benchmarks simply
> because they happen to have kubuntu-desktop installed or left around

Are we honestly optimizing for benchmarks now? I'd rather optimize for
a good user experience, which in the case of Kubuntu requires the use
of CFQ. I couldn't care less about
random-news-site-running-random-benchmarks.

Cheers
Rohan Garg