qemu-io-test: Disable Quorum test when not compiled in. Quorum is not compiled by default: make the quorum 081 test aware of this. Signed-off-by: Benoit Canet <benoit@irqsave.net> Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>