Use TLS v1.1 because v1.2 is not available on CI machines
merge bug26278 into default
Pick most recent TLS version available
Require TLS certificate in TLS authentication tests

Otherwise we get platform-specific failures and even generic client exceptions.
This case is potentially valid but is likely to be really rare (if you use TLS,
you probably also authenticate, using credentials or the certificate).

In the original patch this scenario was expected to fail. We now go back
to square 1.
Don't require peer cert
Use absolute paths here
Merge heads