Apart from dropping the requirement of adding 'include_zones "etc", "zones.d"'
on upgrade to 2.4, we've forgotten to register the local zone directory into
the new ZoneFragment tree.
This fix adds a new function to register the local zones.d directory.
After that the config sync works again.
fixes#9735
By calling `icinga2 troubleshoot collect [--console]` a small file
containing basic application information and a tail of all found logs
and the latest crash report will be created [or displayed].
It does not collect config files at the moment.
refs #3446