Optimize the OvsdbPortUpdateCommand during the ODL reboot/Ovsdb connection

Optimize the OvsdbPortUpdateCommand during the ODL reboot/Ovsdb connection

JIRA: OVSDB-491

When the Compute is connected or flapped, ODL will retrieve all the Ovsdb
configuration from the Compute with MonitorCallBack and process the these configurations
and updates them into the topology operational datastore.
Currently OvsdbPortUpdateCommand will extract the port information that retrieved from
compute and update the same to topology operational datastore. Each port update is resulting in
one database operations.
In scale setup the number ports will be in big number and will result in huge number of
database operations to update these port informations.
It will give us the perfomance improvement if the number of database operations for the
port updates is done per bridge instead of per port, during Ovsdb connection.
This will reduce the number of db operations to number bridges instead of number of port

This review is collect all the Port create commands and update the datastore with
single merge on bridge node.

Signed-off-by: Chandra Shekar S <chandra.shekar.s@ericsson.com>
Change-Id: Ie3ab258fb665d40e92177b4435b1bd72c07fdb81