Another defer reference

There was a posting to squid-users with the following log messages in the
cache log:

2006/08/04 16:01:42| WARNING! Your cache is running out of filedescriptors
2006/08/04 16:01:42| comm_call_handlers(): WARNING defer handler for
fd=12 (desc=HTTP Socket) does not call commDeferFD() - backing off
manually

This patch should fix the second message.

Steven