Ignore .tmp files
Lower default heartbeat setting to 240 seconds

F5 load balancers by default will close TCP connections
that have been idle for 300 seconds.

The choice of the new 240 seconds interval is not
particularly scientific: any < 10 minutes interval
would work, given that heartbeats are sent at
roughly 1/2 the interval. As far as
performance overhead from heartbeats goes, 240
is about as good as 590.
Use 580 seconds as default heartbeat interval

240 seconds gives a theoretiacl 2.5 decrease in server load
(over the previous default of 600 seconds), while
580 gives a ~3% increase.

In a test that involved watching CPU usage 1000 idle connections
I observe effectively no difference between 600 and 580 values.

580 seconds is enough to cause network activity every 290 (< 300) seconds
and hopefully make F5 gear with default timeout settings happy.
Remove tab, ignore .tmp
Merge bug25845
stable to default