Output CLUBB variables on trop_cld_lev when possible

### What is the feature/what would you like to discuss?

This is the same as CAM issue #715, but specifically for CLUBB variables.

I should note that there is no rush on this, I am just trying to provide a record of it as a "to-do" item now.

### Is there anyone in particular you want to be part of this conversation?

@adamrher @bstephens82 @JulioTBacmeister

### Will this change (regression test) answers?

I Don't Know

### Will you be implementing this enhancement yourself?

Any CAM SE can do this