Description of problem:
New method of accessing gluster(RHS) volumes through samba involves the use of vfs plugin for gfapi.
Version-Release number of selected component (if applicable):
this is a new feature and new features don't come into stable release branches by policy. If you want to include vfs_glusterfs you need to patch your samba packages. As it just got into master end of May 2013 it will be part of the next 4.1 release.