Remove unused test fields from VbNvStorage

Confirmed via codesearch that these fields are not used outside of
vboot_reference itself, and the only use inside vboot_reference is one
test which checked that the test error generation itself worked.

BUG=chromium-os:31668
TEST=make && make runtests

Signed-off-by: Randall Spangler <rspangler@chromium.org>
Change-Id: Ic393e126ca2853f7aaff19ffd6fcdbdb1c47689f
Reviewed-on: https://gerrit.chromium.org/gerrit/24895
Reviewed-by: Simon Glass <sjg@chromium.org>
7 files changed