Unable to discover a host into host inventory in disconnected environment

Issue

• While trying to discover a host into the host inventory in disconnected environment, the host fails to fetch the assisted-installer-agent image resulting into a host discovery failing.
• The issue can be ovserved either while discovering the node via discovery ISO or by using automatic way by providing the BMH details.
• The host tried to fetch the assisted-installer-agent image from the public registry registry.redhat.io instead of the local mirror registry.
• The host is not found in the respective InfraEnv even after booting the host from discovery ISO or provising BMC details.