Add two small atms files to allow for testing of zero obs on a rank for the rttov operator#520

BenjaminRuston merged 3 commits intodevelopJCSDA-internal/ufo-data:developfrom

feature/fixRTTOVTLADZeroObsJCSDA-internal/ufo-data:feature/fixRTTOVTLADZeroObsCopy head branch name to clipboard