Addressed issues

Issues addressed in the MKE 3.9.4 release include:

• [FIELD-8086] Fixed an issue wherein during an automatic upgrade of optional components, using a private registry, the worker nodes fail to pre-pull the required images.

• [FIELD-8002] Fixed an issue wherein during a manual upgrade of mandatory components, using a private registry, the worker nodes fail to pre-pull the required images.

• [FIELD-7634] Fixed an issue wherein changes made to the backup schedule did not propogate across all manager nodes.