HUE-2716 [pig] Scripts fail on hcat auth with org.apache.hive.hcatalog.pig.HCatLoader()
Fix for HUE-2716, updating use_hcatalog() in pig's models.py to set hcat credentials
for org.apache.hive.hcatalog.pig.HCatLoader and HCatStorer, in addition to the
soon-to-be-deprecated api's org.apache.hcatalog.pig.HCatLoader and HCatStorer.