I trimmed your code down since I only want to set the header for all the steps in a testcase. I don't see the headerproperty1 or 2 in my headers after running the script. Is there another way to do this? Your original script also didn't work because it has some syntax errors
wsdlTestSteps = testRunner.getTestCase().getTestStepsOfType( com.eviware.soapui.impl.wsdl.teststeps.WsdlTestRequestStep.class ) //only WsdlTestRequest steps
wsdlTestSteps.each{
log.info(it)
it.properties['headerproperty1'].value = ("headerproperty1 value")
it.properties['headerproperty2'].value = ("headerproperty 2 value")
}