NETVIRT-1200: Upstreaming fixes 2

NETVIRT-1200: Upstreaming fixes 2

VM interface IP not advertised to DCGW via BGP

Issue:
When compute server(CSS) is rebooted , the port state was
transitioning from UP->UNKNOWN and UNKNOWN->UP.The check for
original/updated state in InterfaceStateChange listener update() method
prevented the handling of states.

Fix:
When compute reboots, port state transition can have various
combination. Graceful transition would be UP->DOWN->UNKNOWN and
UNKNOWN->DOWN->UP. But as per the logs we saw UP->UNKNOWN and UNKNOWN->UP.
To handle all posible state transition , now State Transition Table is
introduced.

Change-Id: Ibd79866196f085dab30baaa11d8c5c526567e2fd
Signed-off-by: HANAMANTAGOUD V Kandagal <hanamantagoud.v.kandagal@ericsson.com>