Reapplying the dscp changes: No need to restart DB/OVS on changing dscp value.

Reapplying the dscp changes: No need to restart DB/OVS on changing dscp value.

This patch reapplies the changes that were reverted with the commit 59efa47
(Revert DSCP update changes.). It also addresses the problem introduced by
the original commits, cd8fca2 ((jsonrpc: Correctly setting the dscp value
before reconnect.) and b2e18d (No need to restart DB / OVS on changing
dscp value.), that caused numerous unit test failures on some systems (as
diagnosed by valgrind).
With this change there is no need to restart the DB or OVS on configuring a
different value for the manager or controller connection respectively. On
detecting a change in the dscp value on the socket, the previous socket is
closed and a new socket is created and connection is established with the new
configured dscp value.

Signed-off-by: Mehak Mahajan <mmahajan@nicira.com>