base: fix check-raid to handle no or multiple LDs

The latest fix to check-raid was halfway there, by fixing the case where
no configured LDs exist. Unfortunately, there are also cases where no
output at all is printed, we should handle this gracefully as well.

Finally, the current check is very broken in the sense that only reports
errors if the *last* LD is non-optimal. We have boxes with as much as 14
LDs, so we should check all of them. Plus, the "physical device(s)"
comment was completely wrong, as it was counting logical drives.

Change-Id: I3a6709140c9516c3dedce4a2f55374749ffc2b14