System-app pre hook completes even if it doesn't perform any database actions (e.g. installation, migration)

Expected: If the DATABASE_URL environment variable is missing or set incorrectly in the system-app pre hook pod it should fail with some message. 
This appears to also occur with other misconfigurations such as no ORACLE_SYSTEM_PASSWORD env var in the pre hook.

Actual: The pre hook pod completes without any errors and the system-app pod continues to deploy. The system-app pod will then fail due to missing database structure or missing columns.

The issue has only been discovered while using Oracle. See THREESCALE-5758 for why this scenario might happen.