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 fc3946f..35b3095 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -492,6 +492,9 @@
                 default=False,
                 help='Does the test environment support in-place swapping of '
                      'volumes attached to a server instance?'),
+    cfg.BoolOpt('barbican_integration_enabled',
+                default=False,
+                help='Does the test environment support Barbican integration'),
 ]