and make sure logfile_only doesn't mute failures to open logfile

The cache is again protected by a simple mutex and mp_children/mp_next
is protected by mp_mutex. Each monitor_send_children is called holding
the corresponding mp_mutex meaning the whole path from search base to
the current entry is off limits - cn=monitor searches cannot run in
parallel right now.

The code to initialize the TLS context was being bypassed by tool startup,
causing tools to get the wrong default setting. Move it earlier to avoid
being bypassed.

Howard Chu authored Sep 20, 2021 and Quanah Gibson-Mount committed Sep 27, 2021

But skip calls to syslog() if logfile_only is set.

Unused since 2001 2ae02fc1

This was removed in ITS#5540 since there was no EQUALITY matching rule,
but that situation changed in ITS#8341 and we need to add it back.