addons: vrf: Ensures fib rule for local table have higher pref than fib vrf rule

addons: vrf: Ensures fib rule for local table have higher pref than fib vrf rule

Ticket: CM-9541
Reviewed By: Roopa Prabhu
Testing Done: Yes, by installing ifupdown2 deb onto cel-e1031-01

This patch checks if fib rule for local table have higher pref
than vrf table, if not, it deletes fib rule for local table
with lower pref and adds fib rule for local table with
higher pref than vrf table.

This patch also avoid repeated addition of vrf rules on each ifup