svn dies due to not being able to validate the googlecode.com certificate.
hg does not even attempt to validate it.

Fixes #11806.

Change-Id: I84ced5aa84bb1e4a4cdb2254f2d08a64a1ef23f6
Reviewed-on: https://go-review.googlesource.com/12558Reviewed-by: Ian Lance Taylor <iant@golang.org>