Allow running testr in parallel

Instead of always enforcing testr
to run in a single process enable
the more efficent parallel version
by default instead.

Change-Id: Ide288c41356018c99b44a7d3dffd9612ed0d7fbf

anvil/components/base_testing.py

@@ -83,7 +83,7 @@ class PythonTestingComponent(base.Component):
             # NOTE(harlowja): it appears that testr doesn't seem to support all
             # the 'advanced' features (exclusion, coverage?, verbosity, xunit) as
             # nose. Need to verify this...
-            return ['testr', 'run']
+            return ['testr', 'run', '--parallel']
 
         def get_nose_cmd():
             # See: $ man nosetests