CMR-418: Added echo token to header when retrieving index sets.
CMR-418: Added echo token to header when retrieving index sets.

nasa/Common-Metadata-Repository,nasa/Common-Metadata-Repository,nasa/Common-Metadata-Repository,mschmele/Common-Metadata-Repository,nasa/Common-Metadata-Repository,nasa/Common-Metadata-Repository,mschmele/Common-Metadata-Repository,mschmele/Common-Metadata-Repository,mschmele/Common-Metadata-Repository,nasa/Common-Metadata-Repository