As get-pip.py evolves based on pip 10, while we're still using
pip 9, changes in the way it can be used are causing problems.
For example, the ability to use --download is no longer there.
As such, let's pin to a known good version and leave it at that
until we no longer need to use this script. Version 3.2 maps to
pip 7.1.2 which fulfills our needs.
Change-Id: I2a49a407e82c23540cd0aff209bd276c8a303bf0
Closes-Bug: 1779534
e79314ecd4