jqueue: Look at archived jobs when watching

jqueue: Look at archived jobs when watching

First: This enables the use of “gnt-job watch $id” for archived jobs.

Now, the reason for actually making this work is that during
sufficiently large group or node evacuations jobs are archived before
the client gets to poll for their output. This led to situations where
the jobs would finish successfully, but the client reported an error
because it couldn't see the job anymore.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Bernardo Dal Seno <bdalseno@google.com>