cronbuild publish failure: due to race between parallel deploy builds?

For #1967 on Travis I have the 32-bit and 64-bit x86 builds each deploying separately. Despite the race it worked, making me think Travis or Github could handle adding or creating a new release, but this failure makes it seem like the race can result in problems:

https://travis-ci.org/DynamoRIO/dynamorio/jobs/355222956
```
Deploying to repo: DynamoRIO/dynamorio
remote: Counting objects: 35483, done.
remote: Compressing objects: 100% (5993/5993), done.
remote: Total 35483 (delta 30181), reused 34726 (delta 29432), pack-reused 0
Receiving objects: 100% (35483/35483), 23.67 MiB | 18.80 MiB/s, done.
Resolving deltas: 100% (30181/30181), completed with 742 local objects.
From https://github.com/DynamoRIO/dynamorio
* [new tag] release_1_3_1 -> release_1_3_1
* [new tag] release_1_3_2 -> release_1_3_2
* [new tag] release_1_4_0 -> release_1_4_0
* [new tag] release_1_5_0 -> release_1_5_0
* [new tag] release_2_0_0 -> release_2_0_0
* [new tag] release_2_1_0 -> release_2_1_0
* [new tag] release_2_2_0 -> release_2_2_0
* [new tag] release_3_1_0 -> release_3_1_0
* [new tag] release_3_2_0 -> release_3_2_0
* [new tag] release_4.0.1 -> release_4.0.1
* [new tag] release_4_0_0 -> release_4_0_0
* [new tag] release_4_1_0 -> release_4_1_0
* [new tag] release_4_2_0 -> release_4_2_0
* [new tag] release_5_0_0 -> release_5_0_0
* [new tag] release_6_0_0 -> release_6_0_0
* [new tag] release_6_1_0 -> release_6_1_0
* [new tag] release_6_1_0_rc1 -> release_6_1_0_rc1
* [new tag] release_6_1_1 -> release_6_1_1
* [new tag] release_6_2_0 -> release_6_2_0
* [new tag] release_7_0_0_rc1 -> release_7_0_0_rc1
Current tag is: cronbuild-7.0.17605
dpl.3
Deploying application
/home/travis/.rvm/gems/ruby-2.2.7/gems/octokit-4.6.2/lib/octokit/response/raise_error.rb:16:in `on_complete': PATCH https://api.github.com/repos/DynamoRIO/dynamorio/releases/10145729: 422 - Validation Failed (Octokit::UnprocessableEntity)
Error summary:
resource: Release
code: custom
message: Published releases must have a valid tag // See: https://developer.github.com/v3/repos/releases/#edit-a-release
from /home/travis/.rvm/gems/ruby-2.2.7/gems/faraday-0.14.0/lib/faraday/response.rb:9:in `block in call'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/faraday-0.14.0/lib/faraday/response.rb:61:in `on_complete'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/faraday-0.14.0/lib/faraday/response.rb:8:in `call'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/octokit-4.6.2/lib/octokit/middleware/follow_redirects.rb:73:in `perform_with_redirection'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/octokit-4.6.2/lib/octokit/middleware/follow_redirects.rb:61:in `call'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/faraday-0.14.0/lib/faraday/rack_builder.rb:143:in `build_response'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/faraday-0.14.0/lib/faraday/connection.rb:387:in `run_request'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/faraday-0.14.0/lib/faraday/connection.rb:175:in `patch'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/sawyer-0.8.1/lib/sawyer/agent.rb:94:in `call'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/octokit-4.6.2/lib/octokit/connection.rb:154:in `request'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/octokit-4.6.2/lib/octokit/connection.rb:46:in `patch'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/octokit-4.6.2/lib/octokit/client/releases.rb:55:in `update_release'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/dpl-releases-1.9.1/lib/dpl/provider/releases.rb:121:in `push_app'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/dpl-1.9.1/lib/dpl/provider.rb:194:in `block in deploy'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/dpl-1.9.1/lib/dpl/cli.rb:41:in `fold'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/dpl-1.9.1/lib/dpl/provider.rb:194:in `deploy'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/dpl-1.9.1/lib/dpl/cli.rb:32:in `run'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/dpl-1.9.1/lib/dpl/cli.rb:7:in `run'
from /home/travis/.rvm/gems/ruby-2.2.7/gems/dpl-1.9.1/bin/dpl:5:in `'
from /home/travis/.rvm/gems/ruby-2.2.7/bin/dpl:23:in `load'
from /home/travis/.rvm/gems/ruby-2.2.7/bin/dpl:23:in `'
failed to deploy
```

Yet cronbuild-7.0.17605 has both Linux builds and the Windows build so it worked in the end.
Filing this to document the issue.