Don't use java tmp dir for XAR plugin integration tests

ERROR: [withMaven] WARNING Exception executing Maven reporter 'Junit Publisher' / org.jenkinsci.plugins.pipeline.maven.publishers.JunitTestsPublisher. Please report a bug associated for the component 'pipeline-maven-plugin' at https://issues.jenkins-ci.org 
java.lang.IllegalArgumentException: Cannot relativize '/tmp/invalidContent/target/surefire-reports' relatively to '/home/hudsonagent/jenkins_root/workspace/XWiki_xwiki-commons_master'
	at org.jenkinsci.plugins.pipeline.maven.util.XmlUtils.getPathInWorkspace(XmlUtils.java:363)
	at org.jenkinsci.plugins.pipeline.maven.publishers.JunitTestsPublisher.executeReporter(JunitTestsPublisher.java:258)
	at org.jenkinsci.plugins.pipeline.maven.publishers.JunitTestsPublisher.process(JunitTestsPublisher.java:202)
	at org.jenkinsci.plugins.pipeline.maven.MavenSpyLogProcessor.processMavenSpyLogs(MavenSpyLogProcessor.java:125)
	at org.jenkinsci.plugins.pipeline.maven.WithMavenStepExecution$WithMavenStepExecutionCallBack.finished(WithMavenStepExecution.java:1051)
	at org.jenkinsci.plugins.workflow.steps.BodyExecutionCallback$TailCall.onSuccess(BodyExecutionCallback.java:114)
	at org.jenkinsci.plugins.workflow.cps.CpsBodyExecution$SuccessAdapter.receive(CpsBodyExecution.java:368)
	at com.cloudbees.groovy.cps.impl.ValueBoundContinuation.receive(ValueBoundContinuation.java:21)
	at com.cloudbees.groovy.cps.Block$Noop.eval(Block.java:30)
	at com.cloudbees.groovy.cps.Next.step(Next.java:83)
	at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:174)
	at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:163)
	at org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:129)
	at org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:268)
	at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:163)
	at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$101(SandboxContinuable.java:34)
	at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.lambda$run0$0(SandboxContinuable.java:59)
	at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:108)
	at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:58)
	at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:182)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:332)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$200(CpsThreadGroup.java:83)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:244)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:232)
	at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:64)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:131)
	at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
	at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)