git_auto_svn.py: Rewrite http SVN URLs to https
git_auto_svn.py: Rewrite http SVN URLs to https

BUG=435091
TESTED=Ran the following:
git clone https://chromium.googlesource.com/external/webrtc
cd webrtc
git auto-svn
cat .git/config
Verified the URL was using http before this patch, and https after applying it.

R=agable@chromium.org, mmoss@chromium.org

Review URL: https://codereview.chromium.org/745473003

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@293041 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

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