* perl/Amanda/Taper/Scribe.pm: Add await_device method and handle
  cancelling a dump before the device is set.
* perl/Amanda/Taper/Worker.pm: Call scribe wait_device before starting
  the dump.


git-svn-id: https://amanda.svn.sourceforge.net/svnroot/amanda/amanda/trunk@5208 a8d146d6-cc15-0410-8900-af154a0219e0