Some conversion tests need a different (more general) 'expected value' calculation.

[dorchard]

In test_cam_interface.f90, we noticed that some of the expected values are incorrectly calculated in general (although for these specific tests they happen to work). Specifically here:
https://github.com/m2lines/convection-parameterization-in-CAM/blob/testing_routines_dao/tests/test_CAM_interface/test_cam_interface.F90#L465-L467
(which should be doing += 1.0 not =1.0)
and similarly here:
https://github.com/m2lines/convection-parameterization-in-CAM/blob/testing_routines_dao/tests/test_CAM_interface/test_cam_interface.F90#L417-L419
(although this one is perhaps less problematic in this specific case).