qemu-iotests: skip 039 with ./check -nocache

When the qemu-io --nocache option is used the 039 test case cannot abort
QEMU at a point where the image is dirty.  Skip the test case.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/039

@@ -44,6 +44,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 _supported_fmt qcow2
 _supported_proto generic
 _supported_os Linux
+_unsupported_qemu_io_options --nocache
 
 size=128M
 

tests/qemu-iotests/common.rc

@@ -297,6 +297,20 @@ _supported_os()
     _notrun "not suitable for this OS: $HOSTOS"
 }
 
+_unsupported_qemu_io_options()
+{
+    for bad_opt
+    do
+        for opt in $QEMU_IO_OPTIONS
+        do
+            if [ "$bad_opt" = "$opt" ]
+            then
+                _notrun "not suitable for qemu-io option: $bad_opt"
+            fi
+        done
+    done
+}
+
 # this test requires that a specified command (executable) exists
 #
 _require_command()