Add skip for api tests

Change-Id: I67d2596b32063df92092e58bb3803372b22d1492
diff --git a/barbican_tempest_plugin/tests/api/base.py b/barbican_tempest_plugin/tests/api/base.py
index 566f363..c098978 100644
--- a/barbican_tempest_plugin/tests/api/base.py
+++ b/barbican_tempest_plugin/tests/api/base.py
@@ -69,6 +69,8 @@
     @classmethod
     def skip_checks(cls):
         super().skip_checks()
+        if not CONF.service_available.barbican:
+            raise cls.skipException('Barbican is not enabled.')
         api_version_utils.check_skip_with_microversion(
             cls.min_microversion,
             cls.max_microversion,