Pin get-pip.py to 3.2
Pin get-pip.py to 3.2

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: I2fa1c67ecd712364a822edcf7470e5489447d990

openstack/bifrost,openstack/bifrost