MULE-8013: Added connections configuration parameters for incoming and o...

...utgoing requests.
In my opinion default values should be in the XSD to make it clear what will be the expected behaviour when there is no value set.
Is also valid the idea to validate that some arguments are not used depending on other attribute's values. 
In this case, I prefer to add the default value and document that the attribute will be ignored depending on the other attribute's value.