Merge branch 'ipv4-fix-bugs-when-enable-route_localnet'

Shijie Luo says:

====================
ipv4: fix bugs when enable route_localnet

When enable route_localnet, route of the 127/8 address is enabled.
But in some situations like arp_announce=2, ARP requests or reply
work abnormally.

This patchset fix some bugs when enable route_localnet.

Change History:
V2:
- Change a single patch to a patchset.
- Add bug fix for arp_ignore = 3.
- Add a couple of test for enabling route_localnet in selftests.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>