Don't use multiprocessing and OpenMP together in from-samples
requested to merge leo-singer/ligo.skymap:ligo-skymap-from-samples-no-openmp-if-multiprocessing into master
In the KDE clustering and ligo-skymap-from-samples, disable OpenMP
parallelism if Python mulitprocessing parallelism is enabled. This
will prevent the program from spawning an excessive number of
threads.