Decommission an RSE (temporarily)

1. Set the availability_[read || write || delete] settings:

rucio-admin rse update --rse <RSE_IDENTIFIER> --setting availability_read --value 0
rucio-admin rse update --rse <RSE_IDENTIFIER> --setting availability_write --value 0
rucio-admin rse update --rse <RSE_IDENTIFIER> --setting availability_delete --value 0