Fix subnet creating failure in functional test

Noticed sometimes floating ip func test failed[1].

The first mumber of the address seems like cannot
bigger than 223. So specify subnet ranges as the
random number between 0 to 233, maybe it will safer
for our functional tests.

[1]: http://logs.openstack.org/50/418650/12/check/gate-osc-dsvm-functional-ubuntu-xenial/e163f68/console.html#_2017-01-14_06_58_35_930306

Change-Id: I44a23bce851dcf2009c8d77059cf75ed80145fb0

openstackclient/tests/functional/network/v2/test_floating_ip.py

@@ -37,7 +37,7 @@ class FloatingIpTests(base.TestCase):
         # Make a random subnet
         cls.subnet = ".".join(map(
             str,
-            (random.randint(0, 255) for _ in range(3))
+            (random.randint(0, 223) for _ in range(3))
         )) + ".0/26"
 
         # Create a network for the floating ip