GFS2: gfs2_dir_get_hash_table(): avoiding deferred vfree() is easy here...

vfree() is allowed under spinlock these days, but it's cheaper when
it doesn't step into deferred case and here it's very easy to avoid.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>