Fix config-dir for middleware tests

The etc directory from pycadf 0.5 is installed into the virtualenv created
by tox at the top, not inside the library directory. Adjust the location
the audit middleware tests use to find the directory.

Change-Id: I01268c6294ed8799622300a0db01fc836a2f544f
Ignore migrate versioning tables in utf8 sanity check

The migration version tables for alembic and sqlalchemy-migrate should
not be validated to be utf8. This is because these tools are not
explicitly part of the database schema defined in the projects. In certain
configurations it is not possible to ensure these tables will be utf8
character set unless a change to the my.cnf or explicit character set
on table creation is specified.

Change-Id: Ib5c0f93c788afda92aad862e50dc086dc39605f1
Closes-Bug: #1301036