ovn-controller: Add datapath-type and iface-types in chassis:external_ids

ovn-controller: Add datapath-type and iface-types in chassis:external_ids

This patch reads the 'Bridge.datapath_type' column value of the integration
bridge and 'Open_vSwitch.iface_types' column value and sets these in the
external_ids:datapath-type and external_ids:iface-types of Chassis table.

This will provide hints to the CMS or clients monitoring OVN SB DB to
determine the datapath type (DPDK or non-DPDK) configured and take some
actions based on it.

One usecase is, OVN neutron plugin can use this information to set the
vif_type (ovs or vhostuser) during the port binding.

Signed-off-by: Numan Siddique <nusiddiq@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Ryan Moats <rmoats@us.ibm.com>