migrate: cleanup forwarding code
fixing the following two issues:
- the legacy code path was never converted to the new fork_tunnel
signature (which probably means that nothing triggers it in practice
anymore?)
- the NBD Unix socket got forwarded multiple times if more than one disk
was migrated via NBD (this is harmless, but wrong)
for the second issue I opted to keep the code compatible with the
possibility that Qemu starts supporting multiple NBD servers in the
future (and the target node could thus return multiple UNIX socket
paths). currently we can only start one NBD server on one socket, and
each drive-mirror simply starts a new connection over that single
socket.
I took the liberty of renaming the variables/keys since I found
'tunnel_addr' and 'sock_addr' rather confusing.
Reviewed-By: Mira Limbeck <m.limbeck@proxmox.com>
Tested-By: Mira Limbeck <m.limbeck@proxmox.com>
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>