Resolve "A008 (disk usage): don't ERROR if log_directory does not exist"

Description

Trapped error if log_directory does not exist.

Related issue

#236 (closed)

Examples

# do not fail if log_directory does not exist
if $(${CHECK_HOST_CMD} "sudo stat \"$PG_LOG_DIR\" >/dev/null 2>&1"); then
  echo "\"log_directory\":"
  print_df "$PG_LOG_DIR"
fi

Closes #236 (closed)