At least in case of QEMU an IOThread is actually a pool of
threads (see iothread_set_aio_context_params() in QEMU's code
base). As such, it can have minimal and maximal number of worker
threads. Allow setting them in domain XML.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
