Channels are a concept similar to job types. Callers must specify a channel
name when queueing a new job. A list of channels is also specified when
dequeueing a job. The dequeued job's channel will always be from one of the
specified channel. Of course, the job types are also respected. The dequeued
job will also always be from one of the specified type.
Currently, all calls to jobqueue were changed so all queue operations use
an empty channel name and all dequeue operations use a list containing
an empty channel.
Thus, this is a non-functional change.
Signed-off-by: Ondřej Budai <ondrej@budai.cz>
