ocfs2: Add xattr mount option in ocfs2_show_options()

Patch adds check for [no]user_xattr in ocfs2_show_options() that completes
the list of all mount options.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>