Correct legacy rucio_comms include

[veprbl]

It needs to be a package import, but we rely on hacks

Traceback (most recent call last):
  File "swf-testbed/agents/data_agent.py", line 43, in <module>
    from rucio_comms.utils          import calculate_adler32_from_file, register_file_on_rse, RucioUtils
ModuleNotFoundError: No module named 'rucio_comms'

[veprbl]

I think we can just move the two functions inline or to some swf-common-lib.rucio_utils.