Ensure provision_new_database is True by default

In I3e238b6a97769cf0a352f11e718d5d73eebcfa8a, we restored
zzzeek's overlooking the fact that legacy test suites assume
new DBs are provisioned by default in the legacy test base.
However, zzzeek also made this same assumption in Neutron
Ie27cf174fa24c2f479af47335d9ae139fb7d159a which vendors its
own version of test_base in anticipation of some of these newer
features, so it will break once the provision_new_database flag
becomes false.  Favor setting this flag True/False explicitly
and default it to True for compatibility w/ Neutron.

Change-Id: I726cc20481a9bc778b75564526d9245132b43563

oslo_db/sqlalchemy/provision.py

@@ -111,7 +111,7 @@ class DatabaseResource(testresources.TestResourceManager):
     """
 
     def __init__(self, database_type, _enginefacade=None,
-                 provision_new_database=False, ad_hoc_url=None):
+                 provision_new_database=True, ad_hoc_url=None):
         super(DatabaseResource, self).__init__()
         self.database_type = database_type
         self.provision_new_database = provision_new_database

oslo_db/sqlalchemy/test_fixtures.py

@@ -324,7 +324,8 @@ def _get_provisioned_db(self):
         return self._dependency_resources["_db_%s" % self.ident]
 
     def _generate_database_resource(self, _enginefacade):
-        return provision.DatabaseResource(self.driver, _enginefacade)
+        return provision.DatabaseResource(self.driver, _enginefacade,
+                                          provision_new_database=False)
 
     def _setUp(self):
         super(SimpleDbFixture, self)._setUp()
@@ -392,7 +393,8 @@ def __init__(self, url=None):
 
     def _generate_database_resource(self, _enginefacade):
         return provision.DatabaseResource(
-            self.driver, _enginefacade, ad_hoc_url=self.url)
+            self.driver, _enginefacade, ad_hoc_url=self.url,
+            provision_new_database=False)
 
     def _cleanup(self):
         self._teardown_resources()