- Simplify code in askdir.c that waits for creating an appendable

- Simplify code in askdir.c that waits for creating an appendable
  volume so that it can handle multiple returns from the wait
  code.
- Modify the wait code to permit multiple returns.
- Return a zero when autochanger drives is called and
  it is not an autochanger.
- Make rewind_dev() a method taking a DCR as an argument.
  This permits closing and reopening the drive if the
  rewind fails as happens if the drive was loaded while the
  file descriptor was open. This refreshes the file descriptor.
- Remove the ST_OPENED flag and always rely on fd < 0 for knowing
  if the device is open or not.  This should eliminate
  Arnos problem.
- Return error if reserve cannot find at least one suitable device.
- Make wait_for_sysop() return correct state information.
- Fix Win32 state file problem. write was not using compat
  code. This should fix bug #500.

git-svn-id: https://bacula.svn.sourceforge.net/svnroot/bacula/trunk@2703 91ce42f0-d328-0410-95d8-f526ca767f89