Exclude old distros from yum-puppetlabs mirror

The yum-puppetlabs mirror exceeded its 100GB quota as of April 26.
Rather than increase the quota, start excluding packages for old
platforms we don't provide like RHEL5-6 and Fedora F20-27. We could
probably get even more aggressive with it, but this get the
utilization back under 50% which is plenty of headroom for now.

Change-Id: I9665b3a2a89f991f9433fe7f45bc1bb0e0c7632b

modules/openstack_project/files/mirror/yum-puppetlabs-mirror-update.sh

@@ -38,6 +38,20 @@ $K5START rsync -rlptDvz \
     --delete \
     --delete-excluded \
     --exclude="cisco-wrlinux" \
+    --exclude="el/5" \
+    --exclude="el/6" \
+    --exclude="fedora/24" \
+    --exclude="fedora/25" \
+    --exclude="fedora/26" \
+    --exclude="fedora/27" \
+    --exclude="fedora/f20" \
+    --exclude="fedora/f21" \
+    --exclude="fedora/f22" \
+    --exclude="fedora/f23" \
+    --exclude="fedora/f24" \
+    --exclude="fedora/f25" \
+    --exclude="fedora/f26" \
+    --exclude="fedora/f27" \
     $MIRROR/yum/ $BASE
 
 # TODO(pabelanger): Validate rsync process