Add temptest test failing on scenario002 to skiplist

barbican_tempest_plugin.tests.scenario.
test_volume_encryption.VolumeEncryptionTest.
test_encrypted_cinder_volumes_luks
is timing out on centos-8-scenario002-standalone.

Skip this test until the debug/fix is complete.

Change-Id: I9696d94d1541d5525fc7cad7b4ceb5826ac75576
Related-Bug: #1904223

roles/validate-tempest/vars/tempest_skip.yml

@@ -1767,3 +1767,12 @@ known_failures:
       - name: 'queens'
         reason: 'Running on undercloud'
         lp: 'https://bugs.launchpad.net/tripleo'
+  - test: 'barbican_tempest_plugin.tests.scenario.test_volume_encryption.VolumeEncryptionTest.test_encrypted_cinder_volumes_luks'
+    deployment:
+      - 'overcloud'
+    releases:
+      - name: 'master'
+        reason: 'tempest.lib.exceptions.SSHTimeout'
+        lp: 'https://bugs.launchpad.net/tripleo/+bug/1904223'
+    jobs:
+      - tripleo-ci-centos-8-scenario002-standalone