enable manifold checkpoints with --keep-interval-updates
enable manifold checkpoints with --keep-interval-updates

Summary: Useful to enable --keep-interval-updates with Manifold checkpoints

Reviewed By: myleott

Differential Revision: D27577116

fbshipit-source-id: 6d4ae5aaccc07ecaed8ba6a333b6ab78b148187a

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq