This patch fixes the following problems:

- Fixes a problem with an unclear AdvFS message.  When trying to mount an AdvFS
  fileset on a system that did not have AdvFS installed, the following message 
  was displayed:

        No such device

  Now, in similar cases, the following AdvFS message is displayed:

        Cannot mount AdvFS fileset, AdvFS not installed

- Fixes a problem with AdvFS and links in the /etc/fdmns directory.  
  Previously, AdvFS did not ensure that every link in a directory entry pointed
  to a block device.  Now, it does.