agent: configurable host score factors

Allow configuration of host score factors in (usually)
/etc/ovirt-hosted-engine-ha/agent.conf

Change-Id: If485283c133eb517c9a3036ff42d1cd962a1697d
Bug-Url: https://bugzilla.redhat.com/1037654
Signed-off-by: Greg Padgett <gpadgett@redhat.com>