Fix bug, add command, and RFC: drop lock.

97b84f8: simply adds a new command.  Looks like the style you wanted, clue me in if not.
d6d6d0b: the process didn't exit, so don't pretend that it did.
f356bdb: RFC: I do not think we need this lock.  If the channel is closing, that implies the process no longer exists.  If the process no longer exists, it will not send us any events.  Another way: "process is finished" is by definition the last event that a tracee can give us, and thus while we are handling "process is finished" it is not possible for the tracee to send us another event.
No?