Merge remote-tracking branch 'remotes/mdroth/tags/qga-pull-2016-07-07-tag' into staging

qemu-ga patch queue

* add unit tests for guest-exec command set

# gpg: Signature made Tue 07 Jun 2016 21:43:33 BST
# gpg:                using RSA key 0x3353C9CEF108B584
# gpg: Good signature from "Michael Roth <[email protected]>"
# gpg:                 aka "Michael Roth <[email protected]>"
# gpg:                 aka "Michael Roth <[email protected]>"

* remotes/mdroth/tags/qga-pull-2016-07-07-tag:
  tests: start a /qga/guest-exec test

Signed-off-by: Peter Maydell <[email protected]>