fix Service broker error: Malformatted request error in redis gateway

When you attempt to bind one of the community-provided services in this repository to an application in CloudFoundry release 151, you receive the error "CFoundry::ServerError: 10001: Service broker error: Malformatted request". 

These changes to make the bind complete successfully for the redis service are very similar to the recent changes for mongodb and postgresql for the same issue (pull requests 101 and 105).