We use an element remove-serial-console in image elements.
Renaming this element to match. Also renaming allows us to use
the serial console in devtest runs.
See - https://review.openstack.org/#/c/86272/
Change-Id: I8f1138f58d0046ccdeefa3decc45c36d95c6bf4b
Update the systemd serial port element implementation
so that it uses udev rules. Much nicer than
hard coding ttyS0 and ttyS1.
The udev rule only adds real serial device types
(i.e. == 4). See:
define TTY_DRIVER_TYPE_SERIAL 0x0003
from include/linux/tty_driver.h.
Change-Id: I5d7de4815fd09c01693b7da4b8949f22fee20745
