Ensure wayland session set default values

Previous tests were working due to session not being completely stopped
after logging out.
This is now fixed in distro (we don't append values which were already set).
As we don't have Xsession.d files sourced before running the session,
XDG_DATA_DIRS is empty. Only setting our override isn't enough
as the profiles.d check only for an empty variable, and don't set default key
if not empty (as expected).

session

@@ -5,7 +5,19 @@ set -e
 # `dirname "$script_file"`/share/
 # we don't really on readlink -f "$0", as we always want to
 # point to current/ to get latest update applied immediately.
-XDG_DATA_DIRS=$XDG_DATA_DIRS:/snap/communitheme/current/share/
-GTK2_RC_FILES=$GTK2_RC_FILES:/snap/communitheme/current/share/themes/Communitheme/gtk-2.0/gtkrc
+
+# on Wayland, this is the first process setting this env variable
+if [ -z "$XDG_DATA_DIRS" ]; then
+    XDG_DATA_DIRS="/usr/local/share/:/usr/share/"
+fi
+if [ -n "${XDG_DATA_DIRS##*/snap/communitheme/current/share/*}" ]; then
+    XDG_DATA_DIRS=/snap/communitheme/current/share/:"$XDG_DATA_DIRS"
+    export XDG_DATA_DIRS
+fi
+
+if [ -n "${GTK2_RC_FILES##*/snap/communitheme/current/share/themes/Communitheme/gtk-2.0/gtkrc*}" ]; then
+    GTK2_RC_FILES=$GTK2_RC_FILES:/snap/communitheme/current/share/themes/Communitheme/gtk-2.0/gtkrc
+fi
 export GTK2_RC_FILES
+
 gnome-session --session=ubuntu