sweep PathResolver updates from 21.2
Only a handful of commits were in 21.2 not yet in master for PathResolver:
- 9c17f647 allow calibration files over xrootd
- 7259c0f7 Added the EOS paths for the calibration files.
- 9c16e7a9 Adding some trivial updates to remove GCC 8 warnings.
As this is a sweep, stylistic issues, etc. should preferably not be flagged.
This is needed to fix up issues in getting currently disabled tests to work, so marking this as urgent to get it in quickly.