Fix for Bug:399
Bug Description: Northbound doesn't allow priority and multicastPriority values to be set to 255
Changes Made For: Northbound and Southbound allow priority and multicastPriority values to be set betweeen 0 and 255.

Change-Id: I3fb1191ce63b9b1cfb27aae61ba608065514e86e
Signed-off-by: Sachi <sachi.gupta@tcs.com>