* perl/Amanda/ScanInventory.pm: Can changer set_error_to_unknown if a
  slot previously in error succeed.
* perl/Amanda/Taper/Scan/lexical.pm, perl/Amanda/Taper/Scan/oldest.pm:
  Scan one slot for each error message.
* perl/Amanda/Changer/multi.pm (set_error_to_unknown): new function to
  mark as unknown all slot with a given error message.


git-svn-id: https://svn.code.sf.net/p/amanda/code/amanda/trunk@5877 a8d146d6-cc15-0410-8900-af154a0219e0