Remove utils.reset_is_neutron() to avoid races

If a unit test does not call utils.reset_is_neutron() when
it is complete, it may introduce a race condition because
the utils.is_neutron() value is cached to the old result.

This patch removes the utils.reset_is_neutron() and instead
makes sure that we never have a cached value for it.  It
also refactors _is_neutron out of vmwareapi.VMOps because
it cache the result unnecessarily.

Change-Id: I2440e308b00979b31c750513d14608808a295c33
Closes-Bug: #1309043

nova/test.py

@@ -52,6 +52,7 @@ from nova import rpc
 from nova import service
 from nova.tests import conf_fixture
 from nova.tests import policy_fixture
+from nova import utils
 
 
 test_opts = [
@@ -305,6 +306,11 @@ class TestCase(testtools.TestCase):
             objects_base.NovaObject._obj_classes)
         self.addCleanup(self._restore_obj_registry)
 
+        # NOTE(mnaser): All calls to utils.is_neutron() are cached in
+        # nova.utils._IS_NEUTRON.  We set it to None to avoid any
+        # caching of that value.
+        utils._IS_NEUTRON = None
+
         mox_fixture = self.useFixture(moxstubout.MoxStubout())
         self.mox = mox_fixture.mox
         self.stubs = mox_fixture.stubs

nova/utils.py

@@ -1067,11 +1067,6 @@ def is_neutron():
     return _IS_NEUTRON
 
 
-def reset_is_neutron():
-    global _IS_NEUTRON
-    _IS_NEUTRON = None
-
-
 def is_auto_disk_config_disabled(auto_disk_config_raw):
     auto_disk_config_disabled = False
     if auto_disk_config_raw is not None: