Fix netblue30#1498

This fixes an issue from f12c7af where a private-etc filter was added,
which broke atril loading on Ubuntu 17.04 with the message:
"/usr/bin/atril: error while loading shared libraries: libGL.so.1: cannot open shared object file: No such file or directory"

etc/atril.profile

@@ -29,7 +29,7 @@ tracelog
 
 private-bin atril, atril-previewer, atril-thumbnailer
 private-dev
-private-etc fonts
+private-etc fonts,ld.so.cache
 # atril needs access to /tmp/mozilla* to work in firefox
 # private-tmp