In this document:
https://access.redhat.com/documentation/en/red-hat-jboss-enterprise-application-platform/7.0/using-the-red-hat-jboss-enterprise-application-platform-docker-image/#container_entitlements

Should add a step to enable the required yum repository to be able to install subscription-manager-plugin-container.

Just after "To install the RHSM plugin subscription-manager-plugin-container:", add this command as an example:

$ sudo subscription-manager repos --enable="rhel-7-server-optional-rpms"