pid: zone: add zone id to log name
pid: zone: add zone id to log name

When a log path is provided, append the zone id to the log so that each
zone will have its own log file.

Change-Id: I56f92669eda23148127f53fd50e119912a24200b
Signed-off-by: Patrick Venture <36c53fa43f47f3fd67cb2fc38031827244d18a1f@google.com>

openbmc/phosphor-pid-control,openbmc/phosphor-pid-control