OpenSSL: Disable ECDSA cipher suites on Windows XP.

This matches the logic in nss_ssl_util.cc.

Note: this CL has a test which only affects Windows XP. We
have no try coverage on XP, so if the XP bots break, please
revert.

BUG=405630

Review URL: https://codereview.chromium.org/495663002

Cr-Commit-Position: refs/heads/master@{#293214}
6 files changed