confd: fix RpcVersion call

By accident, we sent the node object as call data in this rpc call,
instead the version request (i.e. nothing). This is due to the fact
that the 'call' data comes second, not first in the function argument.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Agata Murawska <agatamurawska@google.com>