[build][centos8] Update versions of dependencies

[build][centos8] Update versions of dependencies

The varnish and intel-cmt-cat v3.x packages have been flagged as insecure.
``dnf builddep collectd`` was installing the deps for the 5.8 version of
collectd from the epel repo, which included these vulnerable packages.
The build scripts for centos 8 have been updated to unstall dependencies
from opstools instead, which provide a newer version of collectd.

Change-Id: I3d2a1496e3524c4bf7bd56ecbd11e7ceeed01f01
Signed-off-by: Slawomir Strehlau <slawomir.strehlau@intel.com>
Signed-off-by: Emma Foley <efoley@redhat.com>