ospfd: Route-tag is not set to external lsas when applying with rmap

ospfd: Route-tag is not set to external lsas when applying with rmap

Description:
Route-tag is not set to external lsas originated by ospf when a routemap
applied by setting a specific tag. When applying a route-map on redistribution,
external lsas will be refreshed if there is any change in the route parametrs
after applying routemap. But changing tag is not handled here.
Added the apripriate fix to correct this.

Signed-off-by: Rajesh Girada <rgirada@vmware.com>