Session limit performance enhancement on central point

The session limit on the central point can now support 1.6 million connections per second (cps) on devices with 10 SPCs. The central point updates the session limit counter when the session ages out. Every session age out triggers a central point delete message and many such delete messages consume more time. The central point session limit performance is enhanced by replacing the central point delete message with specific screen report message and hence, saving the central point memory capacity.