Process and/or announce existing routes when a prefix-list, distribute-

Process and/or announce existing routes when a prefix-list, distribute-
list or filter-list is applied (added or removed) against a neighbor or
peer group. This makes the behavior inline with other configuration changes
such as add or remove of route-map against a neighbor or change of other
settings such as next-hop-self or as-override.

Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>
Reviewed-by: Daniel Walton <dwalton@cumulusnetworks.com>
Reviewed-by: Vipin Kumar <vipin@cumulusnetworks.com>