Revert "virtio_console: Initialize guest_connected=true for rproc_serial"

This reverts commit 8078db78, and
adds a lengthy comment explaining the problem area.

The reverted patch caused opening of ports to fail for rproc_serial.
In probe guest_connected was set to true, but port_fops_open()
fails with -EMFILE if guest_connected already is true.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Acked-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>