Add idempotent_id lines for tests

All tempest tests should have a line to identify the
test with a unique UUID.  This patch adds the line
@decorators.idempotent_id('UNIQUE_UUID')
to the beginning of the test cases, and also adds
a line to tox.ini to check for the proper existence
of this line.

Change-Id: I02b1d7936423d351c7d9b236aaebe54dee3e174a
Depends-On: I18f5c726513b68083d8a5793b8eb391b421b8514
diff --git a/tox.ini b/tox.ini
index 90ca6bb..f100b39 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,9 @@
 commands = python setup.py test --slowest --testr-args='{posargs}'
 
 [testenv:pep8]
-commands = flake8 {posargs}
+commands =
+    flake8 {posargs}
+    check-uuid --package barbican_tempest_plugin
 
 [testenv:venv]
 commands = {posargs}