memento_updater: support downloading non-block-device content

A new parameter --[no]check_block_device is introduced to support channels for
non-block-device like firmware or HWID updaters.

This CL depends on http://gerrit.chromium.org/gerrit/1827 .

Firmware updater execution logic is also removed, to generalize the processing
of non-block-device channels

BUG=chrome-os-partner:4276
TEST=see http://gerrit.chromium.org/gerrit/1827

Change-Id: Ib401f208f7685d51ceda8ce4b0a41e1c054f11ae
Reviewed-on: http://gerrit.chromium.org/gerrit/1887
Reviewed-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
1 file changed