system-test: fix web font corruption

A recent patch added bootstrap support, which includes embedded fonts
for icons.  While other packages handled these additional files correctly,
the system-test deployed "filtered" versions of the font files, resulting
in browsers rejecting the fonts and deplaying the characters with a
regular font.

This patch ensures that the web-fonts, CSS and javascript files are not
affected by dCache filtering.

Target: master
Patch: https://rb.dcache.org/r/7059/
Acked-by: Karsten Schwank
Acked-by: Gerd Behrmann