qemu: add run-with async-teardown capability

qemu: add run-with async-teardown capability

QEMU capability is looking in query-command-line-options response for
...
    {
      "parameters": [
        {
          "name": "async-teardown",
          "type": "boolean"
        }
      ],
      "option": "run-with"
    }
...
allow to use the QEMU option -run-with async-teardown=on|off

Signed-off-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>