Use prefixed URLs path when calling internal Rietveld with OAuth2 auth.
Use prefixed URLs path when calling internal Rietveld with OAuth2 auth.

Internal Rietveld exposes OAuth2 compatible API via /bots/* endpoints, not via
/* as public one does. See crbug.com/476690.

R=maruel@chromium.org
BUG=356813

Review URL: https://codereview.chromium.org/1082033002

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@294793 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

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