PCP: Resolve nested derived metric definitions for devicesmain

Previously these expressions were (incorrectly) silently failing
to evaluate because a derived metric expression was geing nested
which isn't valid.  Now libpcp generates several warnings like:
"Semantic error: derived metric htop.screen.disks.read_await: operand disk.dev.r_await: Illegal nested derived metric"

Fortunately they're all simple expressions so just unwinding the
nesting is the simplest fix.  Add in help text for good measure.

0 files changed, 0 insertions, 0 deletions