command: Trigger updateCache to shut down any active parser threads

command: Trigger updateCache to shut down any active parser threads

If we trigger a shutdown whilst parsing for whatever reason, in some
cases we were not closing down the parser threads. This change
ensures we do so. The function names are not entirely intuitive
but the behaviour is more correct (and commented). The previous bug
with the stdout failure would trigger this one, if there was a cold
cache and parsing was required (but not otherwise).

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>