Update implementation to the new ELP wire format (fix bug 846)

The traffic engineering LCAF encoding format was changed between
revisions -03 and -04 of draft-ietf-lisp-lcaf, please compare the old

    http://tools.ietf.org/html/draft-ietf-lisp-lcaf-03#section-4.9

and new

    http://tools.ietf.org/html/draft-ietf-lisp-lcaf-04#section-4.9

formats.

This patch updates our implementation to use the new format.

Change-Id: Ia2c2aaddd0ab80e537e4ba1e4729de87d2620268
Signed-off-by: Lorand Jakab <lojakab@cisco.com>