Remove force_tenant_isolation=True from test that doesn't need it

Remove extraneous force_tenant_isolation=True tag in trove base

Change-Id: I9e76681172bf55e081870cae8a4d806e8c876de4
diff --git a/tempest/api/database/base.py b/tempest/api/database/base.py
index b68c84a..6e0f431 100644
--- a/tempest/api/database/base.py
+++ b/tempest/api/database/base.py
@@ -25,7 +25,6 @@
     """Base test case class for all Database API tests."""
 
     _interface = 'json'
-    force_tenant_isolation = False
 
     @classmethod
     def setUpClass(cls):