qemu-iotest: Make 077 raw-only

The qemu-io command sequences make the assumption that an unaligned
request on the format layer will be unaligned on the blkdebug layer as
well. This doesn't necessarily hold true for drivers other than raw.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NBenoît Canet <benoit@irqsave.net>

tests/qemu-iotests/077

@@ -38,7 +38,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 . ./common.rc
 . ./common.filter
 
-_supported_fmt generic
+_supported_fmt raw
 _supported_proto generic
 _supported_os Linux