MFC r207878:

MFC r207878:

- Don't return EAGAIN from gv_unload(). It was used to work around the
  deadlock fixed in r207671.
- Wait for worker process to exit at class unload. The worker process
  was not guaranteed to exit before the linker unloaded the module.
- Use 0 as the worker process exit status instead of ENXIO and style
  the NOTREACHED comment.

git-svn-id: svn://svn.freebsd.org/base/stable/8@211065 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f