Add skip for api tests

We should skip tests if  this service environment doesn't consist in environment

Change-Id: I67d2596b32063df92092e58bb3803372b22d1492
Related-Prod: PROD-18238
(cherry picked from commit cc7c63686d02ded823d85012d79826d715208582)
diff --git a/barbican_tempest_plugin/tests/api/base.py b/barbican_tempest_plugin/tests/api/base.py
index 7256a10..26fe533 100644
--- a/barbican_tempest_plugin/tests/api/base.py
+++ b/barbican_tempest_plugin/tests/api/base.py
@@ -65,6 +65,12 @@
     created_objects = {}
 
     @classmethod
+    def skip_checks(cls):
+        super(BaseKeyManagerTest, cls).skip_checks()
+        if not CONF.service_available.barbican:
+            raise cls.skipException('Barbican is not enabled.')
+
+    @classmethod
     def setup_clients(cls):
         super(BaseKeyManagerTest, cls).setup_clients()
         os = getattr(cls, 'os_%s' % cls.credentials[0])