nhrpd: route update support for natoa nbma

nhrpd: route update support for natoa nbma

nhrp_cache_update_route, nhrp_cache_authorize_binding: Fix route update for NAT scenario. When remote_nbma_natoa is already set in the cache entry, binding should be updated to this value and not vc remote nbma, which would be different from the NATted address.

nhrp_shortcut_recv_resolution_rep: Simplify the logic for finding the natoa nbma. Also, install shortcut entries as DYNAMIC type, as suggested in Section 6.2.2 of RFC2332.

nhrp_shortcut_cache_notify: announce the installed route with the correct interface from cache.

Signed-off-by: Ghasem Naddaf <gshirazi@infoblox.com>