[Fix] Regression where content type from swagger @RequestBody does not take precedence

[Mattias-Sehlstedt]

Fixes #3128

Note that I cannot claim to understand the different ways of deriving a request body, due to there being so many different ways of branching the calculation. When debugging the issue I found that the calculation never let go of the default type from the method, and thus json always remained as one of the types, as reported in the issue.

I reintroduced a previous check for if (!methodAttributes.isWithResponseBodySchemaDoc()), that would prevent another calculation round if there is an explicit swagger-core annotation defined (i.e., someone wants to explicitly set the content type that will be present in the specification).

It could be that there are better and more logical ways of realizing this given the changes that were conducted in dcdb1b7.