OFA agent: use hexadecimal IP address in tunnel port name

The remote IP address is used to form the tunnel port name
With some OVS/Linux combinations there is a 15 character limit
on port names, so a name like 'gre-192.168.10.10' does not work.
This fix uses the shorter hexadecimal representation of
the IP address instead.
This problem was reported and fixed for OVS agent.

Closes-Bug: 1294474

Change-Id: Ieab1eb8a5c430f69aff61a317cc28f23ba95ad2d
Merge "OFA agent: use hexadecimal IP address in tunnel port name"