iotests: 086: Add raw format

Raw is as qualified as qcow2 for this test case, add it for more
coverage.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 1450851979-15580-1-git-send-email-famz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

tests/qemu-iotests/086

@@ -38,7 +38,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 . ./common.rc
 . ./common.filter
 
-_supported_fmt qcow2
+_supported_fmt qcow2 raw
 _supported_proto file nfs
 _supported_os Linux