Install a couple of optional feature prereqs in hypervisor plugins.
rootwrap is horribly called indirectly via PATH. The choice, other than fixing
such nonsense, is to force the path in sudo.
TODO:
* python guestfs isn't in pypi, need to specifically install it to not
use the distro package
Change-Id: Iad9a66d8a937fd0b0d1874005588c702e3d75e04
4533eeec1f