periodic/weekly/340.noid: do not use sysrc(8) that depends
on bsdinstall(8) and may be non-functional
for system built WITHOUT_BSDINSTALL. (*)

Also, add a check for jails sharing whole tree with host (path=/)
and do not skip it.

Reported by: Andre.Albsmeier@siemens.com (*)
MFC after: 1 week