MQTT Engine certificates fail to load on startup

This is a known issue with release 4.0.26 and is fixed in the current nightly build

The current workaround, which does not require any changes to the MQTT Engine configuration, is described below:

Add the CA cert chain to the <ignition_install_folder>/data/certificates/supplemental
- Supported formats are DER encoded binary X.509, and Base-64 encoded X.509 (PEM-encoded ASCII)
Restart the Gateway so that the certificates can be used as 'trusted'.