use ClassDefOverride instead of ClassDef to avoid inconsistent-missing-override warning

[smuzaffar]

@ianna, #20534 caused inconsistent-missing-override warnings
https://cmssdt.cern.ch/SDT/cgi-bin/buildlogs/slc6_amd64_gcc630/CMSSW_9_4_X_2017-09-18-1700/SimDataFormats/CaloHit

This PR should fix these

[cmsbuild]

The code-checks are being triggered in jenkins.

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/PR-20570/789

[smuzaffar]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/23050/console Started: 2017/09/18 22:15

[cmsbuild]

A new Pull Request was created by @smuzaffar (Malik Shahzad Muzaffar) for master.

It involves the following packages:

SimDataFormats/CaloHit

@cmsbuild, @civanch, @mdhildreth can you please review it and eventually sign? Thanks.
@rovere this is something you requested to watch as well.
@davidlange6, @slava77 you are the release manager for this.

cms-bot commands are listed here

[cmsbuild]

+1
Tested at: 40eb921
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-20570/23050/summary.html

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:
e133687
You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-20570/23050/git-log-recent-commits
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-20570/23050/git-merge-result

[cmsbuild]

Comparison job queued.

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-20570/23050/summary.html

There are some workflows for which there are errors in the baseline:
10024.0 step 5
The results for the comparisons for these workflows could be incomplete
This means most likely that the IB is having errors in the relvals.The error does NOT come from this pull request

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 26
• DQMHistoTests: Total histograms compared: 2646107
• DQMHistoTests: Total failures: 211
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 2645707
• DQMHistoTests: Total skipped: 189
• DQMHistoTests: Total Missing objects: 0
• Checked 107 log files, 14 edm output root files, 26 DQM output files

[ianna]

Thanks for fixing it.

[davidlange6]

merge