Add possibility to manually setup memory limitation on condor workers

[oshadura]

Running analysis done by Andrzej Novak https://github.com/andrzejnovak/nanocc, we are getting out of memory with standard CoffeaCasaCluster settings.

Traceback (most recent call last):####   ] | 92% Completed | 20min 21.2ss
  File "/opt/conda/lib/python3.8/site-packages/coffea/processor/executor.py", line 975, in __call__
    else _decompress(work.result())
  File "/opt/conda/lib/python3.8/site-packages/distributed/client.py", line 282, in result
    raise exc.with_traceback(tb)
distributed.scheduler.KilledWorker: ('reduce-8c290103790fa30fb1284989b3fd74d2', <WorkerState 'tls://red-c7127.unl.edu:35331', name: htcondor--17405100.0--, status: closed, memory: 0, processing: 2>)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "runner.py", line 471, in <module>
    output = processor.run_uproot_job(sample_dict,
  File "/opt/conda/lib/python3.8/site-packages/coffea/processor/__init__.py", line 104, in _run_x_job
    return run(
  File "/opt/conda/lib/python3.8/site-packages/coffea/processor/executor.py", line 1686, in __call__
    wrapped_out = self.run(fileset, processor_instance, treename)
  File "/opt/conda/lib/python3.8/site-packages/coffea/processor/executor.py", line 1834, in run
    wrapped_out, e = executor(chunks, closure, None)
  File "/opt/conda/lib/python3.8/site-packages/coffea/processor/executor.py", line 985, in __call__
    raise RuntimeError(
RuntimeError: Work item (output reducer) caused a KilledWorker exception (likely a segfault or out-of-memory issue)

How to reproduce:

git clone https://github.com/andrzejnovak/nanocc
git clone https://github.com/andrzejnovak/boostedhiggs.git
pip install scipy --upgrade
cd boostedhiggs
pip install -e .
cd ../nanocc
python runner.py --json metadata/v2x17.json --limit 1  --year 2017 --id test17 --executor dask/casa --chunk 50000 --skip True