add some comment to help you understand the type.

Signed-off-by: samuel deng <mr.dengshuoling@gmail.com>
add the important function to return the dpid of this switch.

Signed-off-by: samuel deng <mr.dengshuoling@gmail.com>
Add self.dpset to maintain the datapathid for query.
Add more DEBUG INFO

Signed-off-by: samuel deng <mr.dengshuoling@gmail.com>
Signed-off-by: samuel deng <mr.dengshuoling@gmail.com>