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

Add support for UNIX sockets in the abstract namespace

# gpg: Signature made Wed 20 May 2020 13:58:43 BST
# gpg:                using RSA key DAF3A6FDB26B62912D0E8E3FBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>" [full]
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>" [full]
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange/tags/socket-next-pull-request:
  qemu-options: updates for abstract unix sockets
  tests/util-sockets: add abstract unix socket cases
  qemu-sockets: add abstract UNIX domain socket support

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