README: update and make less confusing
README: update and make less confusing

The readme is slightly wrong wrt vdsm-hook-faqemu, we fix that by
using correct variables. Additionally, we make the section explaining
hook installation slightly clearer by referring to the engine as
engine instead of manager, and improving the wording.

Change-Id: Ib06c9e47f5cd02be06442a22367d6b2b0fea9c03
Signed-off-by: Martin Polednik <864cc392241c077e6ac82cfafc3cb7cecb8321ba@redhat.com>

oVirt/ovirt-host-deploy,oVirt/ovirt-host-deploy,oVirt/ovirt-host-deploy