Add to tempest conf new  variable

Reguister new variable barbican_integration_enabled in
tempest config -> compute_feature_enabled section

Change-Id: I419b055e5224f498f3c4082bfd88de25a7354ff4
diff --git a/tempest/config.py b/tempest/config.py
index cd9f13f..70f6c15 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -489,6 +489,9 @@
                 help='Does the test environment support attaching a volume to '
                      'more than one instance? This depends on hypervisor and '
                      'volume backend/type and compute API version 2.60.'),
+    cfg.BoolOpt('barbican_integration_enabled',
+                default=False,
+                help='Does the test environment support Barbican integration'),
 ]