Add skip for tests test_signed_image_upload_*

Skip tests if barbican_intagration_enabled = False

Related-PROD: PRODX-360
Change-Id: Ie4fcfc00b0152755e2c82dfd13c6b7e473242871
(cherry picked from commit 09d0f6ff10a83f44b9b999582a94a513ebbb89e8)
diff --git a/barbican_tempest_plugin/tests/scenario/test_image_signing.py b/barbican_tempest_plugin/tests/scenario/test_image_signing.py
index 794d33e..6d9399c 100644
--- a/barbican_tempest_plugin/tests/scenario/test_image_signing.py
+++ b/barbican_tempest_plugin/tests/scenario/test_image_signing.py
@@ -13,6 +13,8 @@
 # under the License.
 
 from oslo_log import log as logging
+import testtools
+
 from tempest.api.compute import base as compute_base
 from tempest.common import utils
 from tempest import config
@@ -29,6 +31,9 @@
 
     @decorators.idempotent_id('4343df3c-5553-40ea-8705-0cce73b297a9')
     @utils.services('compute', 'image')
+    @testtools.skipUnless(
+        CONF.compute_feature_enabled.barbican_integration_enabled,
+        'Barbican integration must be enabled.')
     def test_signed_image_upload_and_boot(self):
         """Test that Nova boots a signed image.
 
@@ -51,6 +56,9 @@
 
     @decorators.idempotent_id('74f022d6-a6ef-4458-96b7-541deadacf99')
     @utils.services('compute', 'image')
+    @testtools.skipUnless(
+        CONF.compute_feature_enabled.barbican_integration_enabled,
+        'Barbican integration must be enabled.')
     def test_signed_image_upload_boot_failure(self):
         """Test that Nova refuses to boot an incorrectly signed image.