allow health check timeout to be configurabled through app attributes
Rename maximum_health_check_timeout to default_health_check_timeout

* Set the default value for default_health_check_timeout in config

Signed-off-by: Aakash Shah <ashah@mines.edu>
Save app health_check_timeout to snapshot

Signed-off-by: Aakash Shah <ashah@mines.edu>
Auto-merge remote-tracking branch 'upstream/master'