[Spring] The java8 parameter is ignored, always behaves as true

Description

The java8 parameter in the spring generator is ignored, always behaves as true. It doesn't matter that it's specified explicitly or not. The generated code always contains Java 8 default interfaces.

Swagger-codegen version

Latest from master.

Command line used for generation

java -jar swagger-codegen-cli.jar generate -i swagger.json -l spring -o build -D hideGenerationTimestamp=true --invoker-package custom.package --model-package custom.package.model --api-package custom.package.api --additional-properties dateLibrary=java8-localdatetime,basePackage=custom,configPackage=custom.swagger,useBeanValidation=true,java8=false

Steps to reproduce

Execute the given command with any valid JSON file.

Suggest a Fix

I guess the issue is in the SpringCodegen.java, but haven't checked thoroughly.