nfsd4: fix xdr4 inclusion of escaped char

Fix a bug where nfsd4_encode_components_esc() includes the esc_end char as
an additional string encoding.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Cc: stable@vger.kernel.org
Fixes: e7a0444a "nfsd: add IPv6 addr escaping to fs_location hosts"
Signed-off-by: J. Bruce Fields <bfields@redhat.com>