Fix heartbeat receiver not working.

Fix heartbeat receiver not working.

65dbbe7a0 added IPv6 support for heartbeat in 4.6. However it
mistakenly bound to only loopback addresses in heartbeat receive
process. Thus heartbeat messages from other watchdog heartbeat sender
were never received. To fix this add AI_PASSIVE flag to hints argument
to getaddrinfo(), which results in binding all network
interfaces. Note that before 4.6, heartbeat receive process uses
INADDR_ANY for bind(), which resulted in binding all network
interfaces too. So there's no big difference between 4.6 and pre-4.6.

Reviewed-by: Bo Peng <pengbo@sraoss.co.jp>
Backpatch-through: v4.6