allow cr repo mirror for early testing

The continuous release centos repo allows
for early testing against pre-released rpms
and updates to minor releases. This is
quite handy when trying to prevent jobs from
going down when CentOS is updated.

https://wiki.centos.org/AdditionalResources/Repositories/CR

Related-Bug: #1788675
Closes-Bug: #1789218
Change-Id: I56e346376976f890899de0cfb47b0612fa5fbb84

modules/openstack_project/files/mirror/centos-mirror-update.sh

@@ -31,7 +31,6 @@ $K5START rsync -rlptDvz \
     --delete-excluded \
     --exclude="atomic" \
     --exclude="centosplus" \
-    --exclude="cr" \
     --exclude="fasttrack" \
     --exclude="isos" \
     --exclude="paas" \