1. A system for restoring a secondary copy of data generated in a local storage management system to a specially configured client in a remote storage management system, the system comprising: a first computing device comprising one or more hardware processors, wherein the first computing device is a component of the remote storage management system and is configured to execute a data agent; a data storage device which is associated with the first computing device and which is also a component of the remote storage management system; wherein the data agent is configured to perform as both: (i) a restore-only client of the local storage management system managed by a local storage manager, based on an authentication certificate and a registry key for communicating with the local storage manager, wherein the registry key associates the data agent and the local storage manager, wherein the authentication certificate and registry key are received from a remote storage manager, and wherein the restore-only client is a destination for restored data from the local storage management system but is not a source of data for storage management operations in the local storage management system, and (ii) a full-function client of the remote storage management system managed by the remote storage manager, wherein the full-function client participates in storage management operations managed by the remote storage manager in the remote storage management system; wherein, as a restore-only client of the local storage management system, the data agent is configured to participate in a restore operation managed by the local storage manager, wherein in the restore operation a secondary copy of data generated in the local storage management system is restored to the data storage device which is associated with the first computing device in the remote storage management system; a second computing device comprising one or more hardware processors, wherein the second computing device is configured to execute a media agent and is a component of the local storage management system that generated the secondary copy; and wherein the media agent is configured to transmit the secondary copy from the local storage management system to the data agent performing as a restore-only client of the local storage management system.