Based on rpmfusion change.

- silence warning
- combine tests in one string.
- dont run VboxClient --vmsvga so it works on both Wayland and xorg

diff -Nurp VirtualBox-6.1.16.orig/src/VBox/Additions/x11/Installer/98vboxadd-xclient VirtualBox-6.1.16/src/VBox/Additions/x11/Installer/98vboxadd-xclient
--- VirtualBox-6.1.16.orig/src/VBox/Additions/x11/Installer/98vboxadd-xclient	2020-10-16 19:30:15.000000000 +0300
+++ VirtualBox-6.1.16/src/VBox/Additions/x11/Installer/98vboxadd-xclient	2021-01-11 17:08:11.159563801 +0200
@@ -21,18 +21,11 @@ for i in $HOME/.vboxclient-*.pid; do
     test -w $i || rm -f $i
 done
 
-if ! test -c /dev/vboxguest 2>/dev/null; then
-   # Do not start if the kernel module is not present.
-   # Execute notify-send in the back-ground to avoid racing with sddm,
-   # as notify-send may wait for sddm to start while it waits for us to exit.
-   notify-send "VBoxClient: the VirtualBox kernel service is not running.  Exiting." &
-elif test -z "${SSH_CONNECTION}"; then
-   # This script can also be triggered by a connection over SSH, which is not
-   # what we had in mind, so we do not start VBoxClient in that case.  We do
-   # not use "exit" here as this script is "source"d, not executed.
+# Do not start if the kernel module is not present; or if this script is
+# triggered by a connection over SSH.
+if [ -c /dev/vboxguest -a -z "${SSH_CONNECTION}" ]; then
   /usr/bin/VBoxClient --clipboard
   /usr/bin/VBoxClient --checkhostversion
   /usr/bin/VBoxClient --seamless
   /usr/bin/VBoxClient --draganddrop
-  /usr/bin/VBoxClient --vmsvga  # In case VMSVGA emulation is enabled
 fi