Add multiple negative test generator support

In order to support different generator styles and sets of tests
a new configuration parameter is introduced to define the negative
test generator class. This can be used to define generators that create
only random values (random fuzzy test) or pattern based values.
With this functionality it is also possible to reduce the amount
of negative tests that are automatically produced.

Change-Id: Icfad55d1eea92dc2a42642b37d34c253c26c0846
Partially-implements: bp fuzzy-test
diff --git a/tempest/tests/negative/test_negative_auto_test.py b/tempest/tests/negative/test_negative_auto_test.py
index 4c59383..27ddc95 100644
--- a/tempest/tests/negative/test_negative_auto_test.py
+++ b/tempest/tests/negative/test_negative_auto_test.py
@@ -16,9 +16,11 @@
 import mock
 
 import tempest.test as test
+from tempest.tests import base
+from tempest.tests import fake_config
 
 
-class TestNegativeAutoTest(test.BaseTestCase):
+class TestNegativeAutoTest(base.TestCase):
     # Fake entries
     _interface = 'json'
     _service = 'compute'
@@ -34,6 +36,10 @@
                        "resources": ["flavor", "volume", "image"]
                        }
 
+    def setUp(self):
+        super(TestNegativeAutoTest, self).setUp()
+        self.stubs.Set(test, 'CONF', fake_config.FakeConfig)
+
     def _check_prop_entries(self, result, entry):
         entries = [a for a in result if entry in a[0]]
         self.assertIsNotNone(entries)