heap_xlog_lock forgets to reset HEAP_XMAX_INVALID

Hi,

While validating my patch for http://archives.postgresql.org/message-id/20160714060607.klwgq2qr7egt3zrr%40alap3.anarazel.de
I noticed that the standby's infomask still had HEAP_XMAX_INVALID set
after replaying a XLOG_HEAP_LOCK record.

That's bad, but not really commonly fatal, because unless prepared
transactions are used, locks don't need to be present / valid after
crash-recovery. But it's clearly something we need to fix.

Given that it's been this way for ages, it's not a blocker for
committing the fix for above URL, but I'll try to get in something today
for that as well. Looks like the minimal fix is just to add
htup->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED);
htup->t_infomask2 &= ~HEAP_KEYS_UPDATED;
to heap_xlog_lock and heap_xlog_lock_updated.

Regards,

Andres