change default of atm_provides_lightning to FALSE -- potentially remove setting the default in CAM

### Issue Type

Other (please describe below)

### Issue Description

Since, currently CTSM can not handle lightning from CAM, the default should be off.

In the future after CTSM is able to do something with lightning it should still be FALSE, until CTSM uses it by default. And as such it probably should be CTSM that controls this setting rather than CAM. So really what should be done is to remove the code in build-namelist here...

``` perl
# for lightning flash freq to CTSM
if ($simple_phys or $aqua_mode) {
add_default($nl, 'atm_provides_lightning', 'val'=>'.false.');
} else {
add_default($nl, 'atm_provides_lightning', 'val'=>'.true.');
}
```

The default in cmeps is FALSE, so not having it in the namelist will keep it as false.

What should be considered is to add a test (or tests) to run with it on, so that the code in CAM to do this isn't broken.

Below on answer changes testing will show a change to answers in the fieldlist of the cpl history files. But, otherwise it'll be bit-for-bit.

Summary:

- [ ] Remove setting of atm_provides_lightning in build-namelist
- [ ] Add at least a test turning it on
- [ ] Will show a change in answers for testing compared to baseline because of a fieldlist different in the cpl history files

### Will this change answers?

No

### Will you be implementing this yourself?

Any CAM SE can do this