Start running all PyPy jobs on Ubuntu Trusty

At this point all the currently voting gate-{name}-pypy jobs which
are working on py3k-precise nodes have been confirmed working on
bare-trusty with the parent change applied to install the
interpreter and headers. Any previously encountered bugs from
earlier testing have been addressed through changes which have since
merged to their respective projects.

Do not merge this until bare-trusty images have been rebuilt with
the parent change merged.

Change-Id: If28dc9b6aadce0fbbf11bb833f0dc4be15c424fa
Merge "Start running all PyPy jobs on Ubuntu Trusty"