GFS2: Don't "get" xattrs for ACLs when ACLs are turned off

This is to match ext3 behaviour. We should not allow getting of
xattrs relating to ACLs when ACLs are turned off.

Reported-by: Nate Straz <nstraz@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>