Several cleanups to tty_info(), better known as Ctrl-T.

Several cleanups to tty_info(), better known as Ctrl-T.

- Only pick up PROC_LOCK once, which means we can drop the PGRP_LOCK
  right after picking up PROC_LOCK for the first time.

- Print the process real time, making it consistent with tools like
  time(1).

- Use `p' and `td' to reference the process/thread we are going to
  print. Only use pick-variables inside the loops. We already did this
  for the threads, but not the processes.