title: Error: "Expected named arguments" in parallel in Jenkins groovy script
body: <p>I have a Jenkins 2.0 pipeline, with a groovyscript like this:</p>
  
  <pre><code>node('nnh561.raijin') {
      stage 'checkout'
      build('trunk/checkout')
  
      stage 'build'
      parallel(
          { build('trunk/build/gfortran') },
          { build('trunk/build/ifort') }
      )
  
  }
  </code></pre>
  
  <p>Each of the individual jobs builds fine, but when I try to run the pipeline, it spits out this error when it hits the parallel step:</p>
  
  <pre><code>java.lang.IllegalArgumentException: Expected named arguments but got [org.jenkinsci.plugins.workflow.cps.CpsClosure2@242d0d3a, org.jenkinsci.plugins.workflow.cps.CpsClosure2@9bf6d64]
      at org.jenkinsci.plugins.workflow.cps.DSL.parseArgs(DSL.java:275)
      at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:110)
      at org.jenkinsci.plugins.workflow.cps.CpsScript.invokeMethod(CpsScript.java:113)
      at groovy.lang.GroovyObject$invokeMethod$0.call(Unknown Source)
      at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
      at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
      at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:151)
      at org.kohsuke.groovy.sandbox.GroovyInterceptor.onMethodCall(GroovyInterceptor.java:21)
      at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:115)
      at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:149)
      at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:146)
      at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:123)
      at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.methodCall(SandboxInvoker.java:15)
      at WorkflowScript.run(WorkflowScript:6)
      at ___cps.transform___(Native Method)
      at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:55)
      at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:106)
      at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:79)
      at sun.reflect.GeneratedMethodAccessor294.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:606)
      at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
      at com.cloudbees.groovy.cps.impl.ClosureBlock.eval(ClosureBlock.java:40)
      at com.cloudbees.groovy.cps.Next.step(Next.java:58)
      at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:154)
      at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$001(SandboxContinuable.java:19)
      at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:33)
      at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:30)
      at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:108)
      at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:30)
      at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:164)
      at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:277)
      at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$000(CpsThreadGroup.java:77)
      at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:186)
      at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:184)
      at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:47)
      at java.util.concurrent.FutureTask.run(FutureTask.java:262)
      at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:112)
      at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
      at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
      at java.util.concurrent.FutureTask.run(FutureTask.java:262)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
      at java.lang.Thread.run(Thread.java:745)
  Finished: FAILURE
  </code></pre>
  
  <p>Any ideas what might be causing something like that?</p>