zk history writer: less verbose zk error logging

* Do not log stack traces for connection losses.
* Use CONNECTIONLOSS instead of APIERROR in test for less spam in logs.
zk registrar: less verbose zk error handling

Do not log stack traces for connection losses.
task runner: remove unused throws declaration
supervisor: less verbose error logging

Do not log stack traces for docker exceptions.
zk updater: log parent path
test: logging: less verbose helios logging

Only log file:line for helios loggers instead of both logger and
file:line.

Also remove unused nopex appender.
child processes: more robust parent monitoring

Monitor whether the parent pid changes. If it does, then the child has
been reparented due to the parent exiting.