Add FORCE_HTTPS_COMMIT_URL to codereview.settings.

This will make it possible to use a https URL when committing
to SVN from from git-svn checkouts created with 'fetch webrtc'
(i.e. from a pure Git mirror in Chrome infrastructure).

This will have effect only after
https://codereview.chromium.org/760903004/ is landed.

BUG=chromium:412012
TESTED=This CL will be committed using git cl dcommit from
a checkout created with 'fetch webrtc', combined
with depot_tools patched with https://codereview.chromium.org/760903004/

Review URL: https://webrtc-codereview.appspot.com/32569004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7766 4adac7df-926f-26a2-2b94-8c16560cd09d