Martin von Zweigbergk <martinvonz@google.com> [Wed, 07 Jan 2015 14:30:40 -0800] rev 23759
test-bundle2-exchange: create temp script in $TESTTMP, not $TESTDIR
The bundle2-pushkey-hook.sh script is currently created in $TESTTMP,
and leaves an untracked file in that directory (tests/) after running.