iotests: Check for quorum support in test 139

The quorum driver is always built in, but it is disabled during
run-time if there's no SHA256 support available (see commit e94867ed).

This patch skips the quorum test in iotest 139 in that case.
Signed-off-by: NAlberto Garcia <berto@igalia.com>
Message-id: 1447172891-20410-1-git-send-email-berto@igalia.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

tests/qemu-iotests/139

@@ -400,6 +400,8 @@ class TestBlockdevDel(iotests.QMPTestCase):
         self.checkBlockDriverState('node1', False)
 
     def testQuorum(self):
+        if not 'quorum' in iotests.qemu_img_pipe('--help'):
+            return
         self.addQuorum('quorum0', 'node0', 'node1')
         # We cannot remove the children of a Quorum device
         self.delBlockDriverState('node0', expect_error = True)