Fixed bug #432: Downtime scheduled as "Nagios Process" and not the Users name 

Previously the comment associated with a scheduled downtime would use a 
hard-coded value of "(Nagios Process)" as the user that scheduled the 
downtime. Now it will use the author from the downtime itself in the comment
associated with the downtime.

If no downtime author is specified (or more accurately, the author field in the
downtime structure is NULL), the system will default to "(Nagios Process)"
as the author of the downtime.
Corrected comparison operator in service freshness check logic.

The service freshness check logic was resetting the expiration after every
short (relative to the freshness threshold) Nagios outage for service 
checks but preserving the expiration if Nagios had been down for a long 
time in comparison with the freshness threshold.

This logic was opposite the host freshness check logic, which has been correct
for quite some time.