Title: zfs_arc_cache: returns OK even if values of arc meta are missing
Level: 1
Component: checks
Version: 1.2.5i4
Date: 1401970608
Class: fix

If a ZFS does not report any data about arc meta, the check up to now did
return UNKNOWN state. Now in this case it returns OK, because this is a valid
state for a ZFS too.

Additional adding PNP templates for the graphs.
