Set the zone if specified in the SOAP request

https://bugzilla.redhat.com/show_bug.cgi?id=1135627

The required zone can be specified in the "parameters" being passed
to CreateAutomationRequest. The attribute name is called miq_zone
@jrafanie I prefer the way this is coded now which allows for a nil zone value to be passed.  it gives the flexibility to specify a specific zone, any zone or default to the zone of the currently server.