[JENKINS-62231] Move start logic to postInitialize to avoid OldDataMo…

[MRamonLeon]

See JENKINS-62231 for full story

To avoid the plugin to fail when loading its configuration if any modification has been done we move the logic from start to postInitialize method. It may help for future versions upgrade/downgrade ability.

@res0nance @fcojfernandez @alecharp @varyvol @rsandell ARggghhhh I cannot even request reviewers

[MRamonLeon]

maybe just load() is needed

[res0nance]

Looks reasonable

[fcojfernandez]

Seems good, but not tested

[MRamonLeon]

The build is failing because the recommendedConfiguration uses jenkins.version=2.164.1 and we updated jenkins.version to 2.176.4. We should use a different configuration or revert the bump of the jenkins.version.

@res0nance at this point, taking into account the discussion about recommendedConfigurations in the pipeline-library, the safest way seems to be to specify directly the configuration we need.

def recentLTS = "2.222.3"
def configurations = [
        // Intentionally test configurations which have detected the most problems
        // Linux - Java 8 with plugin specified minimum Jenkins version
        // Windows - Java 8 with recent LTS
        // Linux - Java 11 with recent LTS
        [ platform: "linux", jdk: "8", jenkins: null ],
        // [ platform: "windows", jdk: "8", jenkins: null ],
        // [ platform: "linux", jdk: "8", jenkins: recentLTS, javaLevel: "8" ],
        [ platform: "windows", jdk: "8", jenkins: recentLTS, javaLevel: "8" ],
        [ platform: "linux", jdk: "11", jenkins: recentLTS, javaLevel: "8" ],
        // [ platform: "windows", jdk: "11", jenkins: recentLTS, javaLevel: "8" ]
    ]

I will try in a new commit, not sure if I have the rights to do that.

[MRamonLeon]

I believe my changes on Jenkinsfile wasn't taken into account

[res0nance]

There seems to be an issue on windows as well, I'll work on it later, right now I'm trying to get the builds going again quickly

[MRamonLeon]

@res0nance would you be able to cut a release with #455 and other improvements? To avoid pain on people upgrading with old ssh clients.