Make LOGDIR configurable for Python processes (See #11943)

Java processes are being explicitly given the OMERO_LOGFILE
variable. Python processes make use of omero.util.LOG_DIR for
choosing a location. Now this is configurable via
`omero.logging.directory`.
Add pointer to master.{out,err} config (See #11943)

The node logging configuration does not make use of the
`${OMERO_*}` variables. Instead, these must be set manually
in the etc/*.cfg files.