Remove phedexnodetocmsname

fixes issue #5360.

This patch builds on #5359 which migrates the WMCore to using sitedb PNNtoPSN. This patch should therefore probably be applied after #5359 as it removes all trace of phedexNodetocmsName from the code base and migrates the unittest that was using it (RequestQuery.py) to the new PNNtoPSN api.