Missing defer/recover/panic idiom in HTTPD service

[corylanou]

We are missing this idiom:

 defer func() {
        if r := recover(); r != nil {
            fmt.Println("Recovered in f", r)
        }
    }()

In the HTTPD service recovery handler:

https://github.com/influxdb/influxdb/blob/master/services/httpd/handler.go#L800

This is allowing queries to panic and bring down the service.