Force boringssl client and server to use draft 22 instead of draft 18.
Other clients (tstclnt from NSS, picotls) support only draft 22.
Disable mint, it only supports draft 21.
Similar to boringssl, reuse the NSS client image for the NSS server test
against the tris client. Bump the NSS version to 3.34.1 gain support
for TLS 1.3 keylogging which is useful while debugging.
Adjust read check to fix intermittent NSS test failures:
https://github.com/cloudflare/tls-tris/issues/58
There is no reason a server can't just send a CloseNotify in its first
flight, and then close the connection without reading the 0-RTT data.
Also, it's not expected of Close to block on reading, and interlocking
with a Read can cause a deadlock.
Fixes NCC-2016-001
