Maintenance: Check for expected squid-conf-tests notifications (#1231)
Sometimes, Squid must accept a configuration file while also logging a
WARNING or even an ERROR message. The new "expect-message" test case
instruction tells test-suite/test-squid-conf.sh to check for a given
expected message while still expecting configuration acceptance.
Two test cases (mgr_passwd.conf and time_units.conf) were enhanced. We
plan to use this feature in future tests already under development.