centos mirror: drop -p from rsync

This appears to be the same thing we saw in Fedora with
Id24196791f80cd99fe8a330fb2c7c6d893fc9995, somehow upstream
directories have started acquiring a setgid bit, which breaks AFS
mirroring

 rsync: failed to set permissions on "/afs/.openstack.org/mirror/centos/8/AppStream/aarch64/os": Permission denied (13)

and when we look

 chmod("AppStream/aarch64/os/Packages", 02755) = -1 EACCES (Permission denied)

Drop the "-p" so we don't try and replicate these permissions.

Change-Id: Ib5db052cdd23e39aecbeead15cf08d4bd7fcab38

playbooks/roles/mirror-update/files/centos-mirror-update

@@ -38,7 +38,7 @@ if ! [ -f $BASE/8 ]; then
 fi
 date --iso-8601=ns
 echo "Running Centos 8 rsync..."
-$K5START rsync -rptDvz \
+$K5START rsync -rtDvz \
     --delete \
     --delete-excluded \
     --exclude="isos" \
@@ -75,7 +75,7 @@ for REPO in $REPOS; do
 
     date --iso-8601=ns
     echo "Running rsync..."
-    $K5START rsync -rptDvz \
+    $K5START rsync -rtDvz \
     --delete \
     --delete-excluded \
     --exclude="atomic" \