futility: updater: always add a \0 when reading files from archives
futility: updater: always add a \0 when reading files from archives

To simplify parsing text files in future we want the archive_read_file
to always return a NULL terminated string on success.

BUG=None
TEST=make; run test
BRANCH=None

Signed-off-by: Hung-Te Lin <8a7fce4940baad93a69f5073b383c85deed9d9c4@chromium.org>
Change-Id: I0dd0105971a80d857a1b05d9680b34b42dbff7e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3612645
Reviewed-by: Julius Werner <4d12f06cff3725783b352157673a720bc67c4afe@chromium.org>
Commit-Queue: Julius Werner <4d12f06cff3725783b352157673a720bc67c4afe@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot