The next patch will add another client that wants to merge dirty
bitmaps; it will be easier to refactor the code to construct the QAPI
struct correctly into a helper function.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200521192137.1120211-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>