Add test coverage for TLS version negotiation.

Test all pairs of client and server version, except for the ones that require
SSLv3 client support in runner.go. That is, as yet, still missing.

Change-Id: I601ab49c5526cd2eb4f85d5d535570e32f218d5b
Reviewed-on: https://boringssl-review.googlesource.com/1450
Reviewed-by: Adam Langley <agl@google.com>
2 files changed