Fix bugs in test_migrations.py

This fixes two related issues in nova/tests/test_migrations.py.

First, the snake_walk flag was only set to True for the first test run
out of TestMigrations. setUp() always set snake_walk to False initially
then would only update the value if TEST_DATABASES was empty.
TEST_DATABASES was only empty during the setUp() of the first test.
Fix this by resetting test_databases before each test.

Second, because snake_walk was always False when test_walk_versions
performing the snake walk version of the database migrations was never
tested and broken. When downgrading from version X to version X -1 of a
database version X must be passed to the migration tool as version X
contains the downgrade path for that particular version. Set the correct
versions when snake walking the DB migrations.

Part of blueprint grizzly-testtools

Change-Id: I8d4d9ee8efe46b4690dd6cbe95879e88aaeb0b5a

0 files changed, 0 insertions, 0 deletions