network/route: drop Route object even if we fail to remove the route

network/route: drop Route object even if we fail to remove the route

If we could not remove a route, then previously the corresponding
Route object was never removed, as it was freed only when we receive
remove notification from the kernel. So, we might confused that the
route still exists and being removed, and might block reconfiguring
the route.

With this change, even if we fail to remove a route, the corresponding
Route object will be freed.

This is the one for routes of 56a995fe8e50b2432ff930ed0431cc70adbe492d.