reintroduce missing lseek() for header-less files

[fwyzard]

PR description:

Fix a problem encountered reading legacy FED RAW data files in "file list" mode.

PR validation:

Reading legacy files now works.

[fwyzard]

Thanks to @smorovic for the fix.

[cmsbuild]

@fwyzard, CMSSW_11_0_X branch is closed for direct updates. cms-bot is going to move this PR to master branch.
In future, please use cmssw master branch to submit your changes.

[fwyzard]

@cmsbuild, please test

[cmsbuild]

The code-checks are being triggered in jenkins.

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-27982/11873

• This PR adds an extra 28KB to repository

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-run-pr-tests/2502/console Started: 2019/09/12 17:45

[cmsbuild]

A new Pull Request was created by @fwyzard (Andrea Bocci) for master.

It involves the following packages:

EventFilter/Utilities

@perrotta, @mommsen, @cmsbuild, @emeschi, @slava77 can you please review it and eventually sign? Thanks.
@Martin-Grunewald this is something you requested to watch as well.
@davidlange6, @slava77, @fabiocos you are the release manager for this.

cms-bot commands are listed here

[cmsbuild]

+1
Tested at: 361bb72
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3c68d1/2502/summary.html

[cmsbuild]

Comparison job queued.

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-3c68d1/2502/summary.html

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 4 differences found in the comparisons
• DQMHistoTests: Total files compared: 34
• DQMHistoTests: Total histograms compared: 2957224
• DQMHistoTests: Total failures: 2
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 2956881
• DQMHistoTests: Total skipped: 341
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 33 files compared)
• Checked 145 log files, 15 edm output root files, 34 DQM output files

[slava77]

+1

for #27982 361bb72

• code changes are in online-specific code EventFilter/Utilities/src/EvFDaqDirector.cc, which is not in the reco responsibility (the package is shared with daq).
• jenkins tests pass

[mommsen]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @davidlange6, @slava77, @smuzaffar, @fabiocos (and backports should be raised in the release meeting by the corresponding L2)

[fabiocos]

+1