Do not crash rrd_toggle when switching to tmpfs
Running on the 12-03-2018 nightly build of TrueNAS 11.2 (stable, internal)
Two time now on this build, upon making changes to a pool I begin getting collectd errors and cannot see reporting graphs. First time I saw it was upon adding a SLOG to my data pool. Second time was upon adding an L2ARC device to the same pool. Problem resolves after reboot and verifying the "System->System Data->Reporting Database" option is checked
Dec 3 10:38:24 tn03-a uwsgi: [reporting.rrd:163] Failed to generate graph: b"ERROR: opening '/var/db/collectd/rrd/localhost/aggregation-cpu-sum/cpu-idle.rrd': No such file or directory\n"
Dec 3 10:38:26 tn03-a uwsgi: [reporting.rrd:163] Failed to generate graph: b"ERROR: opening '/var/db/collectd/rrd/localhost/zfs_arc/cache_ratio-arc.rrd': No such file or directory\n"
SYstem is currently running a performance benchmark so I didn't take a debug yet.