Edited test_rad_loss_rate unit test to give 100% test coverage of calc_rad_loss().
Edited test_rad_loss_rate unit test to give 100% test coverage of
calc_rad_loss().

dpshelio/sunpy,dpshelio/sunpy,Alex-Ian-Hamilton/sunpy,Alex-Ian-Hamilton/sunpy,Alex-Ian-Hamilton/sunpy,dpshelio/sunpy