We have been seeing failures in parallel Py34
tests caused by the test database being set up more
than once.
The existing mechanism is not thread-safe.
Add a lock around the database setup to ensure
the it is ever executed by only one thread.
Partially implements: blueprint trove-python3
Change-Id: I68aba50d60b912384080911a6f78283f027c4ee3
Petr Malik
94b716142a