Recent regressions in the code base removed permission setting of
/dev/kvm to root:kvm 660 permissions which are default for CentOS's
version of libvirt.

Also Libvirt must be able to read its cnofiguration file, which was
previously 600 root:root.  Now its 644 root:root so its always readable.
This is fine, since this file doesn't contain any secret information.

Change-Id: Id87cf5da8e37bc5bb613ce919d0293803d0fe5ed
Closes-Bug: #1500733