If the Change-Id in the description is different from the one fetched
from Gerrit, automatically set the right one instead of asking the
user to do so.

Change-Id: I0f681d9e7d98f3ed50adc4b6e4929981530e901c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2101368
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Anthony Polito <apolito@google.com>