Description of problem:
In our Ansible playbooks we are doing a four-step process for db migrations, like this:

beaker-init --check
(if check indicates changes are needed)
beaker-init --user... --background
wait for pid file to disappear
beaker-init --check

This works well for migrating existing databases. But for deploying a fresh environment from scratch, it will fail on the final check step.

Version-Release number of selected component (if applicable):
beaker-server-23.0-0.git.248.ede6acc

How reproducible:
easily, with a fresh environment (empty db)

Steps to Reproduce:
1. Configure /etc/beaker/server.cfg to point at a new, empty database containing no tables
2. Run beaker-init --check
3. Run beaker-init --user admin --password '' --email something

Actual results:
Fails with an exception:
Traceback (most recent call last):
  File "/usr/bin/beaker-init", line 9, in <module>
    load_entry_point('bkr.server==23.0.git.248.ede6acc', 'console_scripts', 'beaker-init')()
  File "/usr/lib/python2.6/site-packages/bkr/server/tools/init.py", line 378, in main
    return doit(opts)
  File "/usr/lib/python2.6/site-packages/bkr/server/util.py", line 178, in decorated
    return func(*args, **kwargs)
  File "/usr/lib/python2.6/site-packages/bkr/server/tools/init.py", line 413, in doit
    upgrade_db(metadata)
  File "/usr/lib/python2.6/site-packages/bkr/server/tools/init.py", line 265, in upgrade_db
    run_alembic_operation(metadata, upgrade)
  File "/usr/lib/python2.6/site-packages/bkr/server/tools/init.py", line 317, in run_alembic_operation
    env_context.run_migrations()
[...]
sqlalchemy.exc.NoSuchTableError: `recipe_task`

Expected results:
Initial beaker-init --check should report that the database needs upgrading.
Subsequent beaker-init should then populate it correctly, not die with an exception.

Additional info:
The exception occurs because the initial beaker-init --check seems to silently create an alembic_version table (with no rows). This means the subsequent beaker-init invocation thinks the database is *not* empty and instead tries to follow the pre-0.19 inspection logic to determine the version, which then fails as above. In fact the database is just empty and should be populated from scratch.

So we either need to make beaker-init ignore the presence of alembic_version when considering whether the database is empty, or we need to make beaker-init --check not silently create the alembic_version table.

I would prefer the latter since beaker-init --check promises to make no changes to the database, although we are clearly violating that promise right now.