scan: add an option to determine whether or not to reconnnect ghost

On BFT fixtures, the machine ID for a given BFT fixture is always the
same no matter we scan mlb serial number or not. Add an option to
reconnect ghost only if needed.

BUG=chromium:464624
TEST=manually

Change-Id: Ib4d005475ffe540df0010b9c89e996a8ed26c0ad
Reviewed-on: https://chromium-review.googlesource.com/305104
Commit-Ready: Wei-Ning Huang <wnhuang@chromium.org>
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
Reviewed-by: Pin-chih Lin <johnylin@chromium.org>
1 file changed