Cause: When starting with -f and N monitors, only displays with number <= N were set to fullscreen
Consequence: For guests with sparse displays enabled (e.g. 1 & 4), display number 4 was not set to fullscreen
Fix: When started in fullscreen mode (-f), we now always auto-configure the guest to match the client configuration (e.g. if client has 2 monitors, we enable display 1 and 2 on guest and disable any other displays)
Result: There is always one screen for each client monitor and they are all fullscreen.