Merge branch 'stable-3.9'

* stable-3.9:
  Fallback to public organization information
  Redirect to login on anonymous access to profile pages
  Detect the default branch during the repo import from GitHub
  Bump plugin and Gerrit to v3.9.0-rc5
  Do not import changes refs from GitHub
  Bump to v3.9.0-rc4 and reuse FakeHttpServletRequest/Response
  Refresh GitHub groups upon Gerrit successful login

Change-Id: I8242d270b9e5ff0ca8e221d0b426a337e7710c12