Only re-exec on config change or HUP
Only re-exec on config change or HUP

There are 2 things at play here. First the logic added in
4cfeb28d12295154f1b57308022283cc2eaab079 is no longer needed
because our initial sleep time is very low and increases
gradually up to the max.

2nd, I'm proposing that we avoid reexecing unless the config
file actually changes. Not re-execing will give us the option
to optimize os-collect-config for some long running collectors
(like zaqar websockets).  Also, Os-collect-config updates would
already be handled by packaging restarts and or other deployment
system changes anyways.

Change-Id: I04b2752d007089f72af42c88c4249c3e11c8346f

openstack/os-collect-config