Similar to the uinput module, install the testcases/ tree of modules
only on test images.
BUG=chromium-os:37353
TEST=daisy test image build has modules, production does not.
CQ-DEPEND=I16eee5afd1664f0ab4a9ab48b6cb2beaa6f30017
Change-Id: I5e7a48936b3fb45f49ff7ca4d592d46150c5610c
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39920
Reviewed-by: Chris Sosa <sosa@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
