Drop root for Horizon service
Drop root for Horizon service

Drop root privileges for Horizon service.  It is necesssary to set
a capability on the filesystem to allow binding to port 80 as a
non-root user.  I have tested this works correctly from a registry
on both CentOS and Ubuntu.

Change-Id: I4c26f28bb28b6633784e6842f3423a2425332c27
Partially-Implements: blueprint drop-root

dardelean/kolla-ansible,toby82/kolla,limamauricio/mykolla,mrangana/kolla,rahulunair/kolla,toby82/kolla,intel-onp/kolla,negronjl/kolla,nihilifer/kolla,rahulunair/kolla,negronjl/kolla,dardelean/kolla-ansible,limamauricio/mykolla,limamauricio/mykolla,mandre/kolla,openstack/kolla,mandre/kolla,GalenMa/kolla,coolsvap/kolla,coolsvap/kolla,dardelean/kolla-ansible,toby82/kolla,nihilifer/kolla,tonyli71/kolla,coolsvap/kolla,stackforge/kolla,mrangana/kolla,negronjl/kolla,stackforge/kolla,openstack/kolla,tonyli71/kolla,stackforge/kolla,GalenMa/kolla,intel-onp/kolla,mandre/kolla