Simplify code that parses ifa_flags.

When parsing an RTM_NEWADDR or RTM_DELADDR, ifaddr is always
present (unless the message is invalid). So ifaddr->ifa_flags is
always known before any attributes are parsed.

Bug: 155005831
Test: atest NetworkStackNextIntegrationTests:IpClientIntegrationTest continues to apss
Change-Id: Id1998faccca7d81c1b7f3e85e4912aa22919e94a
1 file changed