tests: Fix bound

Ensure we do not negative values except for -1 (unlimited).

Change-Id: I9a0184ed54054c6466833df24dfbe9ca7d1b454b
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

nova/tests/unit/api/openstack/compute/test_limits.py

@@ -57,7 +57,7 @@ def fake_get_project_quotas(context, project_id, usages=True):
     }
 
     return {
-        k: {'limit': v, 'in_use': v // 2}
+        k: {'limit': v, 'in_use': max(-1, v // 2)}
         for k, v in absolute_limits.items()
     }