Follow redirects downloading pip

Curl didn't follow HTTP Redirects and Github now redirects in some cases...
Specifically raw.github.com here in the get_pip download.

Change-Id: Ic35485083988beabcfa2c2dc21b2c3d4639b3302
Merge branch 'pip-redirect' into dt-test
Merge branch 'conf-tempest' into dt-test