[ACS441] Merge hotfix/4.4-kvm-diskcache

[Wido den Hollander]

Hi Daan,

Could you please merge in hotfix/4.4-kvm-diskcache into 4.4?
It's already in master, but this solves a issue which could prevent 
Instances from starting. Ran into it myself just now while testing 4.4.1

Wido