Some expected Sabre exceptions are now logged with DEBUG level

These exceptions are now logged with DEBUG level:
- "not authenticated" (this wasn't logged before, but is logged with DEBUG now for convenience)
- "precondition failed": #7479 
- "file not found": #7541 (mostly caused by Android client checking for file existence)

Please help testing these @enoch85 @binarykitchen @moscicki
Please review @schiesbn @icewind1991 @DeepDiver1975