route/addr: consider CACHEINFO in addr_compare()/nl_object_diff()

Indicate this change of behavior with the capability
NL_CAPABILITY_ROUTE_ADDR_COMPARE_CACHEINFO.

This is a behavioral change as we now consider an additional
field when comparing addresses.

Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Thomas Haller <thaller@redhat.com>