SecurityContext does not clear the credentials of a SOAP-Gateway in FSW

Issue

• SecurityContext does not clear the credentials of a SOAP-Gateway. Consecutive calls to the gateway add the credentials of each call. If we want to extract the credentials later in the exchange we get wrong(previously added) credentials.
  Cause: SecurityContext is a InheritableThreadLocal, so the object is reused for each call with the same thread (http thread).

• Credentials in the SecurityContext should be empty on each call of the InboundHandler (SOAP).

• The problem is a result of a misbehavior of the class org.switchyard.handlers.SecurityHandler.
  The SecurityHandler handles the lifecycle of the SecurityContext. and is responsible for cleaning up the credentials. This is not handled correctly.