Bug#916398: sddm: Wayland autologin sometimes fails - probable tty1 race

["Rebecca N. Palmer" <rebecca_palmer@zoho.com>]

Control: tags -1 patch

That works (starts successfully with the desktop on tty1) - due to the 
intermittent nature of the bug I can't be sure it's gone, but if we're 
right about the cause it should be.

Full sddm.service tested:

[Unit]
Description=Simple Desktop Display Manager
Documentation=man:sddm(1) man:sddm.conf(5)
# Change this if you want to start sddm in a different tty
Conflicts=getty@tty7.service getty@tty1.service
After=getty@tty7.service getty@tty1.service

After=systemd-user-sessions.service systemd-logind.service

# If using tty1 and plymouth, sddm will fail till plymouth stops
# consider using:
## After=plymouth-quit.service
# or to forcefully stop plymouth and start earlier:
## Conflicts=plymouth-quit-wait.service
## After=plymouth-start.service plymouth-quit-wait.service
## OnFailure=plymouth-quit.service

[Service]
# temporary safety check until all DMs are converted to correct
# display-manager.service symlink handling
ExecStartPre=/bin/sh -c '[ "$(cat /etc/X11/default-display-manager 
2>/dev/null)" = "/usr/bin/sddm" ]'
ExecStart=/usr/bin/sddm
Restart=always
RestartSec=1s
EnvironmentFile=-/etc/default/locale