Use condor pool in jobsub_rm commands if condor_host is not provided in launch script

[LTrestka]

POMS currently can't find schedds that are within the dune condor pool. Users are instructed to set _condor_COLLECTOR_HOST in their launch scripts if not using the default pool.
But in case they forget, we can maintain a list of condor collectors, and determine which one a schedd belongs by running:
'condor_status -schedd -pool $collector' at the start of the service, and storing the results in a dictionary.