[PATCH] Improve the logging for "squid -z" when "cache_dir" is not configured

Hi all,

The patch adds a log message when users runs "squid -z" without
"cache_dir" configured. It is described in bugzilla #3728.

http://bugs.squid-cache.org/show_bug.cgi?id=3728

Eliezer told me I should put here rather than leaving it at bugzilla.
Thanks, Eliezer!

The patch is attached.

Best,
Tianyin

--
Tianyin XU,
http://cseweb.ucsd.edu/~tixu/