Add error handling to smoke test cleanup.

 * DefaultClientSmokeTest.tearDownClass was previously calling
   delete() on test resources without error handling.  Since the
   intent of the method is to remove test resources, a NotFound
   exception indicating that the resource has already been
   removed can safely be ignored.

Change-Id: Idd289d2f3ce4133c49b0c882304d6ad6695a7396
diff --git a/tempest/smoke.py b/tempest/smoke.py
index 68d0927..1e7da8e 100644
--- a/tempest/smoke.py
+++ b/tempest/smoke.py
@@ -56,9 +56,15 @@
             LOG.debug("Deleting %r from shared resources of %s" %
                       (thing, cls.__name__))
 
-            # OpenStack resources are assumed to have a delete()
-            # method which destroys the resource...
-            thing.delete()
+            try:
+                # OpenStack resources are assumed to have a delete()
+                # method which destroys the resource...
+                thing.delete()
+            except Exception as e:
+                # If the resource is already missing, mission accomplished.
+                if e.__class__.__name__ == 'NotFound':
+                    continue
+                raise
 
             def is_deletion_complete():
                 # Deletion testing is only required for objects whose