MULE-7326: Can't use WebService consumer with operation without parameters

Changed behaviour of WS Consumer: if the operation to be consumed requires no input parameters, then the payload will be ignored and a request with one empty XML element will be sent (the one required by the operation).
(cherry picked from commit 4b6c8d9)
MULE-7368: SoapAction header is not being set in WS Consumer for Soap 1.2 web services
(cherry picked from commit 92400af)