The uninstall here has been around since
Ibb4b42119dc2e51577c77bbbbffb110863e5324d. At the time, there might
have been conflicts between packaged and installed pip. We don't need
it today; get-pip.py keeps itself separate enough in /usr/local on all
platforms. Thus we can also remove the suse/centos special-casing.
python3-pip is in the RPM list so we don't need to
re-install for Fedora.
Add a note on why we are over-installing pip.
Remove some old setuptools workarounds that are commented out.
Change-Id: Ie3cb81a8ff71cf4b81e23831c380f83b0381de71
8dac135cb8