prescribed aerosols and oslo_aero

[mvertens]

In build-namelist the following section of code hard-wires the variable prescribed_aerosols. Is this still needed?

   if( $chem =~ /_oslo/){
    $prescribe_aerosols = $FALSE;
    print " ==> Using Oslo aerosols: PRESCRIBED AERO = FALSE (not yet implemented) \n"
}

[oyvindseland]

Given that prescribed_aero now in CAM is only defined as bam, the hard-coded version should not be needed. If relevant it can be included as a "bam_oslo" at some point but given the cloud and optical parameterisation I think the parameterisation will look entirely different.
Before the hard-wiring is removed the it should be tested if the existing test covers _oslo or whether it has to be included at the same point where the aero=_mam is setting prescribed_aero = false. As far as I can see prescribed_aero = true as the default.