This reverts commit 71d10ea626.
It was unnecessary once the offending wheel got removed from PyPI,
and this never worked anyway. It was preventing the ability to boot
new nodes, erroring thusly:
./configure_mirror.sh: line 25: /tmp/pip.conf: Permission denied
Deleting the images to which the change was applied returned
nodepool to being able to boot new nodes again.
Change-Id: I0841c6a5a26cf5be22e2d8fea861bdceb0393842