First try and making the nagios module NOOPpable

Could you review this and make sure I'm doing this the right way?

My approach was 

````
if we were going to exit with a failure AND we're in check_mode:
    exit with changed=False
else(if: we were about to do something):
    exit with changed=True (but don't do anything)
````

Also, some automatic trailing whitspace cleanup snuck in