client: Print milliseconds in log message timestamps
client: Print milliseconds in log message timestamps

- When printing timestamps for log messages, print the millisecond offset
within the second, using the same format as PK

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr