Fix permission errors from liveinst exit

We switched to policykit to run Anaconda on Live media where it is
started by liveuser instead of root. However, the pkexec will run the
same script as root and after anaconda ends, the original script will
continue execution as liveuser which is expected to raise permission
errors.

To fix this, stop the script execution after the pkexec call.

Resolves: rhbz#2314607

Reviewed-by: Ray Strode (halfline)

data/liveinst/liveinst

@@ -26,6 +26,7 @@ if [ "$(id -u)" -ne 0 ]; then
     xhost +si:localuser:root
     unset XAUTHORITY
     pkexec "$0" "$@"
+    exit $?
 fi
 
 # pkexec clears DBUS_SESSION_BUS_ADDRESS from environment