Docker users were losing their license activation on every update because
/etc/machine-id changes when the container is recreated.
Changes:
- Store persistent encryption key in /data/.license-key (survives container updates)
- Fall back to machine-id for backwards compatibility with existing installations
- Existing users only need to re-enter their key once, then it persists forever
Fixes issue reported by customer upgrading from RC to v5.0.0.
rcourtman
f1853e354b