fix: skip log files with deleted volumes in filer backup (#3720)
When filer.backup or filer.meta.backup resumes after being stopped, it may
encounter persisted log files stored on volumes that have since been deleted
(via volume.deleteEmpty -force). Previously, this caused the backup to get
stuck in an infinite retry loop with 'volume X not found' errors.
This fix catches 'volume not found' errors when reading log files and skips
the problematic file instead of failing. The backup will now:
- Log a warning about the missing volume
- Skip the problematic log file
- Continue with the next log file, allowing progress
The VolumeNotFoundPattern regex was already defined but never used - this
change puts it to use.
Fixes#3720
1b13324fb7