Revert "Set XDG_CURRENT_DESKTOP for the started session"

This reverts commit a54293e5d194ecca841de408e33ab7ee6023c55f.
Revert "Revert "Set XDG_CURRENT_DESKTOP for the started session""

This reverts commit cef5b2a2d0e0bda01f400278e469f7384de8d26d.
Revert "Revert "Revert "Set XDG_CURRENT_DESKTOP for the started session"""

This reverts commit 32546ed5c02eb8eacbc7824a46112542d62048fd.