Add a qmp command that can trigger guest announcements.
It uses its own announce-timer instance, and parameters
passed to it explicitly in the command.
Like most qmp commands, it's in the main thread/bql, so
there's no racing with any outstanding timer.
Based on work of Germano Veit Michel <germano@redhat.com> and
Vladislav Yasevich <vyasevic@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
a06cd488d8