Fix 'fetch blink' recipe for proper management.
Fix 'fetch blink' recipe for proper management.

This both ensures that 'git auto-svn' has been properly run, and also that
the Blink checkout is appropriately 'unmanaged'.

R=dpranke@chromium.org, mmoss@chromium.org
BUG=289742

Review URL: https://codereview.chromium.org/1186053007

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@295916 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

svn2github/chromium-depot-tools,svn2github/chromium-depot-tools,svn2github/chromium-depot-tools