Add duplicated idempotent_ids checks

Add a shell script for duplicated idempotent_ids checks,
this is a copy from Neutron repo.

Change-Id: I0a00f9830a7d29812bcccc257a1bea8a6477d9e8
diff --git a/tox.ini b/tox.ini
index 74c85e5..dbd0526 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,11 @@
 commands = python setup.py test --slowest --testr-args='{posargs}'
 
 [testenv:pep8]
-commands = flake8 {posargs}
+commands =
+  sh ./tools/misc-sanity-checks.sh
+  flake8 {posargs}
+whitelist_externals =
+  sh
 
 [testenv:venv]
 commands = {posargs}