rajrangan

The bug is in the [formParams.mustache](https://github.com/swagger-api/swagger-codegen/blob/master/modules/swagger-codegen/src/main/resources/JavaSpring/formParams.mustache) its missing the handling of required flag in the "isFile" condition. Should be changed to: `{{#isFormParam}}{{#notFile}}@ApiParam(value = "{{{description}}}"{{#required}}, required=true{{/required}}{{#allowableValues}}, allowableValues="{{#values}}{{{.}}}{{^-last}}, {{/-last}}{{#-last}}{{/-last}}{{/values}}"{{/allowableValues}}{{#defaultValue}}, defaultValue="{{{defaultValue}}}"{{/defaultValue}}) @RequestParam(value="{{baseName}}"{{#required}}, required=true{{/required}}{{^required}},...

@wing328 will you be able to review this change?