Specify tunneling type for OVS agent

Parameter agent/tunnel_types does not defaults to 'gre' as ovs/tunnel_type
hence it has to be set explicitly.

Change-Id: I332f311526b69bd5d16c8bdc5010c80c8ae22de5
Fixes: rhbz#1069215
(cherry picked from commit 9793db3a4066ec813e3b0035610fc3688cf3e450)
Merge "Specify tunneling type for OVS agent" into havana