Teamconcert fails to check out code when the builds are requested from RTC.

This is due to changes in Jenkins 1.655, specifically in JENKINS-33467 and this commit.

There, it is mentioned that some plugins break due to the new changes, and need to be changed. Teamconcert suffers the same issue, it assumes that CauseAction.getCauses is not inmutable in this line.

See fix from another plugin.

Please fix it ASAP, as we can't update jenkins.

Full stacktrace:
RTC : checkout...
RTC : Build initiated by request from RTC
FATAL: RTC : checkout failure: null
java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableCollection.add(Collections.java:1075)
at com.ibm.team.build.internal.hjplugin.RTCScm.checkout(RTCScm.java:1158)
at hudson.scm.SCM.checkout(SCM.java:485)
at hudson.model.AbstractProject.checkout(AbstractProject.java:1269)
at hudson.model.AbstractBuild$AbstractBuildExecution.defaultCheckout(AbstractBuild.java:607)
at jenkins.scm.SCMCheckoutStrategy.checkout(SCMCheckoutStrategy.java:86)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:529)
at hudson.model.Run.execute(Run.java:1738)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:410)
ERROR: RTC : checkout failure: null