staticd: Backend cofiguration code to fix table-id problem

staticd: Backend cofiguration code to fix table-id problem

problem: table-id gets overwritten for a given route.

RCA: table-id was getting overwritten from the NB layer,
     So route was getting installed with the latest table-id.

Fix: make the table-id as the key in the NB layer.
     This will program the route in zebra correctly.

- Removed the table-id modify callbacks.
- Moved the validate and apply table-id changes to path-list creation

issue #7347

Signed-off-by: vishaldhingra <vdhingra@vmware.com>