This is a follow-on to I3761dd9d2ab752e66bcccdd2434405f11535b95f where
I misunderstood what "linear" was doing. What was really intended was
to stop both the python2 and python3 builds copying to AFS at the same
time. "linear" just means the *tasks* start at the same time across
hosts; not that they run serially. To do that you want the (aptly
named) "serial" specifier on the playbook.
Add this so we do the copies sequentially
Change-Id: I4f8a2f2c6c8164e7ea207f8e4b286e06df0b13dd
b34c442fcb