iotests: Fix 237 for Python 2.x

math.ceil() returns an integer on Python 3.x, but a float on Python 2.x.
range() always needs integers, so we need an explicit conversion on 2.x
(which does not hurt on 3.x).

It is not quite clear whether we want to support Python 2.x for any
prolonged time, but this may as well be fixed along with the other
issues some iotests have right now.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190210145736.1486-3-mreitz@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

tests/qemu-iotests/237

@@ -224,7 +224,7 @@ with iotests.FilePath('t.vmdk') as disk_path, \
             iotests.log("= %s %d =" % (subfmt, size))
             iotests.log("")
 
-            num_extents = math.ceil(size / 2.0**31)
+            num_extents = int(math.ceil(size / 2.0**31))
             extents = [ "ext%d" % (i) for i in range(1, num_extents + 1) ]
 
             vm.launch()