Because pip install role is used as meta of the repo_build, we have
circular dependencies before anything could be done.
This cleans up the hosts of the --isolated flags, and therefore can
properly bootstrap pip.
Change-Id: I85cba02628dc454947c0bb798764f5f3955dc48b
Signed-off-by: Jean-Philippe Evrard <jean-philippe.evrard@rackspace.co.uk>
(manual forward port)