Skip safeguards for the database named "test"

[abitrolly]

GitLab AutoDevops provides database for testing that is accessible through postgres host name, and that makes safeguards fail with RemoteDatabaseUrl error. But the database itself is named test, so it should be possible to relax safeguard rules to include this possibility,

DEBUG: DATABASE_URL = postgres://user:testing-password@postgres:5432/test

https://docs.gitlab.com/topics/autodevops/stages/#auto-test

[abitrolly]

Fixed with allowlist to allow test, test.sqlite, test.sqlite3 database names in DATABASE_URL, and also DATABASE_URL to be unset:

    DatabaseCleaner.url_allowlist = [ %r{/test(\.sqlite3?)?$}, nil ]

See also #728