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 to as 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'.