Gerrit seems to concatenate several commit messages on uploading branch
creation CLs. Now we pass the commit message of the branch commit to
the upload script to prevent this.

NOTRY=true

Bug: v8:8546
Change-Id: Ia4673261aad2f40bcda4384889a0428039adae74
Reviewed-on: https://chromium-review.googlesource.com/c/1367454Reviewed-by: Sergiy Belozorov <sergiyb@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58092}