Wss4jHandler: override securement password using the message context

[cachescrubber]

Wss4jHandler: override securement password using the message context

Analog to the ``securementUsername, allow to override the `securementPassword` using the `MessageContext` in order to efficiently support per-request credentials.

  @Override
  public boolean handleRequest(MessageContext messageContext) throws WebServiceClientException {
    AlternativeCredentials alternativeCredentials = context.get();
    // override default interceptor username/password using per-request messageContext.
    if (alternativeCredentials != null) {
      messageContext.setProperty(Wss4jSecurityInterceptor.SECUREMENT_USER_PROPERTY_NAME,
          alternativeCredentials.getUsername());
      messageContext.setProperty(Wss4jSecurityInterceptor.SECUREMENT_PASSWORD_PROPERTY_NAME,
          alternativeCredentials.getPassword());
    }
    return super.handleRequest(messageContext);
  }

This is a non breaking change, test are added accordingly.

[corneil]

Thank you @cachescrubber