Fix [#35728] "Load Factory Settings" changes temp fonder to "/temp/\"

This was actually being reset to "/tmp\".

Initialisation for the temp dir was missing after the userpref reload.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57479 954f8c5b-7b00-dc11-b283-0030488c597c