bug#42575: Missing icons in i3

[Jonathan Brielmaier]

I have an annoying issue here whith missing icons in i3. It is installed
via the system configuration as well as `mate-desktop-service-type`.

i3 session
==========

When I log into i3 from slim and open a program like caja it's missing
almost all it's icon.

Having a closer look what happens:

```
caja --gtk-debug=all
[..]
look up icon dir
/run/current-system/profile/share/icons/hicolor/16x16/actions
[..]
```
It only looks up in /run/current-system/profile/share/icons/hicolor

The strange thing is after I once started mate-appearance-properties and
close it after wards, the icons do appear in caja et. al.

MATE session
============

When I do the same inside a running MATE session the icons appear as
expected.