We will soon need to dequeue a job using its ID. This commit adds ability
to do that to the Jobqueue interface. As always, the fsjobqueue implementation
is slightly naive but it should fine for the usecases that it's designed for.
Signed-off-by: Ondřej Budai <ondrej@budai.cz>
This is backwards compatible, as long as the timeout is 0 (never
timeout), which is the default.
In case of the dbjobqueue the underlying timeout is due to
context.Canceled, context.DeadlineExceeded, or net.Error with Timeout()
true. For the fsjobqueue only the first two are considered.
