Use IANA codepoints for Tunnel Encapsulation types

Highlights:

- No changes to vRouter agent code
- Changes are backward compatible with older vRouter agents and CNs
- Xmpp encapsulation string for udp translated to 2 communities
- Xmpp encapsulation string for vxlan translated to 2 communities
- IANA and pre-standard communites for udp translated to 1 xmpp string
- IANA and pre-standard communites for vxlan translated to 1 xmpp string

Change-Id: I5d64282f81409a0805c2f5d97818b5a7649636bd
Closes-Bug: 1373559