Changes to trigger flow re-compute on route Add/Delete

Maintain references to the routes which were ignored due to more specific
route in flow processing, which will be used to trigger flow re-compute
when route is deleted or an new more specific route is avialable.

Update test-cases to accomodate changes.
Added test-case for route add.

Change-Id: I6d263f86018b1e8e5ebb93dffee424c7e9cddcad
Merge "Changes to trigger flow re-compute on route Add/Delete"