Add db_version command to keystone-manage

The db_version command simply looks at the database and prints the
version to which the database has been migrated.

Change-Id: I50098bf1aa6d57883cc9acc0c4d09d9c8448db7f
run_tests.sh should use flake8 (bug 1180609)

Existing flags (e.g. --pep8) are intentionally left alone.

Change-Id: I300aaee17294b88c7d1ba4daad462af407c67d4f
Merge "Add db_version command to keystone-manage"
Merge "run_tests.sh should use flake8 (bug 1180609)"