TestAcquireNodeForm.test_storage_with_named_constraints is flaky

[Gavin Panella]

It has failed in several unrelated branches. I've only observed it fail when landing to trunk via Tarmac.

FAIL: maasserver.tests.test_node_constraint_filter_forms.TestAcquireNodeForm.test_storage_with_named_constraints
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_StringException: Traceback (most recent call last):
  File ".../maasserver/tests/test_node_constraint_filter_forms.py", line 824, in test_storage_with_named_constraints
    self.assertGreaterEqual(disk0.size, 10 * 1000 ** 3)
  File "/usr/lib/python2.7/dist-packages/unittest2/case.py", line 947, in assertGreaterEqual
    self.fail(self._formatMessage(msg, standardMsg))
  File "/usr/lib/python2.7/dist-packages/unittest2/case.py", line 415, in fail
    raise self.failureException(msg)
AssertionError: 6000000000L not greater than or equal to 10000000000