ovs-agent: use hexadecimal IP address in tunnel port name

The remote IP address is used to form the tunnel port name when
the ovs-agent is used with the ML2 plugin. 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.

Change-Id: I58caf54219130159525b5a6492eaa451062c2ff5
Closes-Bug: 1281098
Merge "ovs-agent: use hexadecimal IP address in tunnel port name"