Tests fail confusingly without XDS

[ndevenish]

Running tests without XDS present give:

        for step in ["XYCORR", "INIT", "COLSPOT", "IDXREF"]:
>           lastrecord = open("%s.LP" % step).readlines()[-1]
E           FileNotFoundError: [Errno 2] No such file or directory: 'XYCORR.LP'

fast_dp/autoindex.py:106: FileNotFoundError

This is because run_job doesn't check and provides no way to tell if the process actually ran, so autoindex just carries on as if it's worked:

fast_dp/fast_dp/autoindex.py

Line 98 in 4ea4775

log = run_job("xds_par")