server: use generalized commando socket for worker tasks commands

server: use generalized commando socket for worker tasks commands

Allows to extend the use of that socket in the future, e.g., for log
rotate re-open signaling.

To reflect this we use a more general name, and change the commandos
to a more clear namespace.

Both are actually somewhat a breaking change, but the single real
world issue it should be able to cause is, that one won't be able to
stop task from older daemons, which still use the older abstract
socket name format.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>