When changing memtune limits to unlimited with AFFECT_CONFIG, the
values in virDomainDef are set to PARAM_UNLIMITED, which causes the
whole <memtune> to be formatted. This can be changed in all drivers,
but it also makes sense to use the default (0) as another value for
"unlimited", since zero memory limit makes no sense.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
