Simplify Seat::displayStopped

[Vogtinator]

It tried to be smart and actively switch to a display if a reuse happened. This is not necessary and implemented in a rather fragile way, resulting in errors in some cases.

[Vogtinator]

FTR, here's what happened previously:

Mar 21 13:36:50 localhost.localdomain sddm-greeter[4473]: Reading from "/usr/share/xsessions/plasma5.desktop"
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Message received from greeter: Login
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Reading from "/usr/share/xsessions/plasma5.desktop"
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Will reuse session "20"
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Session "/usr/share/xsessions/plasma5.desktop" selected, command: "/usr/bin/startplasma-x11" for VT 5
Mar 21 13:36:50 localhost.localdomain sddm-helper[4514]: [PAM] Starting...
Mar 21 13:36:50 localhost.localdomain sddm-helper[4514]: [PAM] Authenticating...
Mar 21 13:36:50 localhost.localdomain sddm-helper[4514]: [PAM] Preparing to converse...
Mar 21 13:36:50 localhost.localdomain sddm-helper[4514]: [PAM] Conversation with 1 messages
Mar 21 13:36:50 localhost.localdomain sddm-helper[4514]: [PAM] returning.
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Authenticated successfully
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Reused session "20"
Mar 21 13:36:50 localhost.localdomain sddm-helper[4514]: [PAM] Asked to close the session but it wasn't previously open
Mar 21 13:36:50 localhost.localdomain sddm-helper[4514]: [PAM] Ended.
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Auth: sddm-helper exited successfully
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Greeter stopping...
Mar 21 13:36:50 localhost.localdomain sddm-helper[4452]: Signal received: SIGTERM
Mar 21 13:36:50 localhost.localdomain sddm-helper[4452]: [PAM] Closing session
Mar 21 13:36:50 localhost.localdomain sddm-helper[4452]: pam_unix(sddm-greeter:session): session closed for user sddm
Mar 21 13:36:50 localhost.localdomain sddm-helper[4452]: [PAM] Ended.
Mar 21 13:36:50 localhost.localdomain systemd[1]: session-21.scope: Deactivated successfully.
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Auth: sddm-helper exited with 255
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Greeter stopped. SDDM::Auth::HelperExitStatus(255)
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Socket server stopping...
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Socket server stopped.
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Display server stopping...
Mar 21 13:36:50 localhost.localdomain systemd-logind[1093]: Session 21 logged out. Waiting for processes to exit.
Mar 21 13:36:50 localhost.localdomain systemd-logind[1093]: Removed session 21.
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Display server stopped.
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Running display stop script  ("/usr/share/sddm/scripts/Xstop")
Mar 21 13:36:50 localhost.localdomain sddm[3971]: SDDM::Display(0x201d000) 5 stopped
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Jumping to "20"
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Removing display SDDM::Display(0x201d000) ...
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Jumping to VT 0
Mar 21 13:36:50 localhost.localdomain sddm[3971]: VT mode didn't need to be fixed
Mar 21 13:36:50 localhost.localdomain sddm[3971]: Couldn't initiate jump to VT 0: No such device or address

[arrowd]

I bumped into this when implementing user switching for SDDM+ConsoleKit. The switch in the "reuse" case is indeed not needed, however I can't completely test this due to #1803