Stop using configure block in seed-github-ci.Jenkinsfile

[jlebon]

I think all the knobs in

coreos-ci/jobs/seed-github-ci.Jenkinsfile

Lines 53 to 87 in 65efc68

	// things which don't seem to have a nice DSL :(
	configure {
	it / sources / data / 'jenkins.branch.BranchSource' / strategy {
	properties(class: 'java.util.Arrays\$ArrayList') {
	a(class: 'jenkins.branch.BranchProperty-array') {
	'org.jenkinsci.plugins.workflow.multibranch.DurabilityHintBranchProperty' {
	// we don't care about durability for these CI
	// jobs. we should be able to interrupt and
	// restart from scratch whenever
	hint('PERFORMANCE_OPTIMIZED')
	}
	}
	}
	}
	it / sources / data / 'jenkins.branch.BranchSource' / source << {
	traits {
	'org.jenkinsci.plugins.github__branch__source.BranchDiscoveryTrait' {
	strategyId(1)
	}
	'org.jenkinsci.plugins.github__branch__source.OriginPullRequestDiscoveryTrait' {
	strategyId(1)
	}
	'org.jenkinsci.plugins.github__branch__source.ForkPullRequestDiscoveryTrait' {
	strategyId(1)
	// allow testing of PRs from project contributors
	trust(class: 'org.jenkinsci.plugins.github_branch_source.ForkPullRequestDiscoveryTrait\$TrustContributors')
	}
	}
	}
	it / sources / data / 'jenkins.branch.BranchSource' / buildStrategies {
	'jenkins.branch.buildstrategies.basic.ChangeRequestBuildStrategyImpl' {
	ignoreTargetOnlyChanges(true)
	}
	}
	}

can now be represented natively in job DSL. Let's do that to make it less obscure.

Job DSL API on CoreOS CI: https://jenkins-coreos-ci.apps.ocp.fedoraproject.org/plugin/job-dsl/api-viewer/index.html