[gerrit] CreateAndEditChange: Don't attempt to edit single-line commit message
[gerrit] CreateAndEditChange: Don't attempt to edit single-line commit message

This results in a 409.

Change-Id: If851efd668bfa281255267335bcfb967feb92ccd
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/394220
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot