Gerrit git cl land: add warning if Commit-Queue label exists.
Gerrit git cl land: add warning if Commit-Queue label exists.

BUG=612727
R=agable@chromium.org

Review-Url: https://codereview.chromium.org/2089683002

CoherentLabs/depot_tools,CoherentLabs/depot_tools,primiano/depot_tools,primiano/depot_tools,primiano/depot_tools