Merge remote-tracking branch 'remotes/berrange/tags/qcrypto-next-pull-request' into staging

Add support for PSK credentials with TLS

# gpg: Signature made Tue 03 Jul 2018 13:04:51 BST
# gpg:                using RSA key BE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>"
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>"
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange/tags/qcrypto-next-pull-request:
  crypto: Implement TLS Pre-Shared Keys (PSK).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>