Check Expect-CT at connection setup

This CL adds an Expect-CT check to ShouldRequireCT(), with an option to send
reports if the host is configured with Expect-CT.

This CL is missing a test for ProofVerifierChromium, which I'm omitting because
all the tests for that file are mysteriously disabled and I'm not sure why.

BUG=679012

Review-Url: https://codereview.chromium.org/2850033002
Cr-Commit-Position: refs/heads/master@{#469686}
12 files changed