Merge remote-tracking branch 'remotes/kraxel/tags/pull-vnc-20150520-1' into staging

vnc: misc fixes.

# gpg: Signature made Wed May 20 09:32:45 2015 BST using RSA key ID D3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"

* remotes/kraxel/tags/pull-vnc-20150520-1:
  qemu-sockets: Report explicit error if unlink fails
  vnc: Tweak error when init fails
  vnc: Don't assert if opening unix socket fails
  ui: remove check for failure of qemu_acl_init()
  Strip brackets from vnc host

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