qemu-traditional: disable msitranslate by default

qemu-traditional: disable msitranslate by default

msitranslate is known to cause problems with some device drivers,
because it sets the real device in MSI mode while making the guest think
is actually in legacy interrupts mode. Some drivers are able to spot this
inconsistency and break (Nvidia drivers for example).

Disable the option by default.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: George Dunlap <george.dunlap@eu.citrix.com>