Backport secondary input source improvements from 7_5_X

[wmtan]

Improvements to the secondary input source, back ported from 7_5_X, as requested at Core Software meeting:

1. skipEvents parameter now supported in sequential mode (AKA deterministic mode)
2. sequential mode now loops back to first file after the last file
3. First file opened is randomized.
   Items 1) and 2) are needed to support the avoidance of duplication in the use of premixed pileup.
   This is a back port of PR's Secondary input source improvements/fixes #9091, Remove cerr left in inadvertently #9155, and Skip all entries (per file) at once, not one at a time. #9163 combined, not including the unit test enhancement, which is not being back ported.

[cmsbuild]

A new Pull Request was created by @wmtan for CMSSW_7_4_X.

Backport secondary input source improvements from 7_5_X

It involves the following packages:

IOPool/Input

@cmsbuild, @Dr15Jones, @nclopezo can you please review it and eventually sign? Thanks.
@wddgit this is something you requested to watch as well.
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@Degano you are the release manager for this.
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[Dr15Jones]

please test

[Dr15Jones]

+1

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes or unless it breaks tests. This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @smuzaffar

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes or unless it breaks tests. This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @smuzaffar

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @smuzaffar

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-9181/7730/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_4_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @smuzaffar

[davidlange6]

+1