ipv4: Notify route after insertion to the routing table

Currently, a new route is notified in the FIB notification chain before
it is inserted to the FIB alias list.

Subsequent patches will use the placement of the new route in the
ordered FIB alias list in order to determine if the route should be
notified or not.

As a preparatory step, change the order so that the route is first
inserted into the FIB alias list and only then notified.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>