Qemu unconditionally reports a UUID, which depending on the qemu version
is either all-null (which is incorrect but harmless) or contains a single
bit set for all controllers.  In addition it can also optionally report
a eui64 which needs to be manually set.  Disable namespace identifiers
for Qemu controlles entirely even if in some cases they could be set
correctly through manual intervention.

Reported-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>