Make Rapid Code Distribution feature configurable by group
Originally, when we were planning on introducing the Rapid Code Distribution service to jobsub, the idea was to have all experiments use it and ONLY it in the future. The --use-cvmfs-dropbox option was only meant to be temporary.
It has come to our attention that MARS will, for security reasons, need to still use resilient. So the best way to handle this is to keep resilient, but have the default dropbox mode be to use Rapid Code Distribution. Then, if we make this configurable in the .ini file by group, we could set the default for the MARS groups as resilient.