[Mailman-Developers] Non-queue runners should not create var/queue/* directories

[Sandesh Agrawal]

enqueue() in switchboard.py create a .pck file for each injected
message in var/queue/* directory.
Say a message injected in incoming queue will have a .pck file in var/queue/in

But for 'lmtp' and 'rest' runners , if we do not need the creation of
var/queue/lmtp and var/queue/rest directories, is there a need for
calling enqueue() ?