This test is not suitable anymore since the naming convention has changed in diags to be the same as MMO

if several members, oce will exist for previous members whereas sstsssmld rather for the followings so that lstfiles can be empty

if only one chunk, cdo mergetime is not useful and it would not work because the input and output files would have the same name

oce needs to be before sstsssmld so that oce is not already in the workdir when sstsssmld is treated