On weston-launch exit we see errors such as:
  failed to restore keyboard mode: Invalid argument
  failed to set KD_TEXT mode on tty: Invalid argument

This has been resolved by making sure the tty file descriptor
does not get closed. However, the ioctrl's KDSKBMODE/KDSETMODE
and VT_SETMODE still fail with -EIO:
  failed to restore keyboard mode: Input/output error
  failed to set KD_TEXT mode on tty: Input/output error

It turns out the reason for this lies in some very particular
behavior of the kernel, the separation of weston-launch/weston
and the fact that we restore the tty only after the weston
process quits: When the controlling process for a TTY exits,
all open file descriptors for that TTY are put in a hung-up
state! For more details see this systemd-logind issue:
https://github.com/systemd/systemd/issues/989



We can work around by reopening the particular TTY. This allows
to properly restore the TTY settings such that a successive VT
switch will show text terminals fine again.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>