minidiag: Fix button initialization errors in memory tests

Call log_page_init(ui) to initialize button states in memory tests.
Add TODO comments for splitting out log_page_update().

BUG=b:173772273
BRANCH=zork
TEST=Build locally

Signed-off-by: Hsuan Ting Chen <roccochen@chromium.org>
Change-Id: Icc5504bfcbfefc264a01289cc7988e97064bc8fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2552308
Reviewed-by: Meng-Huan Yu <menghuan@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>