staging: lustre: llite: drop acl from cache

Commit b8a7a3a6

 change get_acl() for posix xattr to always cache
the ACL which increases the reference count. That reference count
can be reduced by have ll_get_acl() call forget_cached_acl() which
it wasn't. When an inode gets deleted by Lustre the POSIX ACL
reference count is tested to ensure its 1 and if not produces an error.
Since forget_cached_acl() was not called Lustre started to complain.
This patch changes ll_get_acl() to call forget_cached_acl().

Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>