title: Zuul -> Eureka Server, Basic Authentication issue
body: <p>I am able to hit the service, if the flow doesn't contain Basic Authorization.</p>
  
  <p>If i use Basic Authorization, it throws "message": "Full authentication is required to access this resource"</p>
  
  <p>Below are my observations:</p>
  
  <p>In ZuulFilter, run() method, i get value for 
  request.getHeader("Authorization")  --> Basic c29tOnNvbzz==</p>
  
  <p>but once it reaches the Micro Service, i am getting  value as 'null',
   request.getHeader("Authorization") --> null</p>
  
  <p>Using Spring Boot version : 1.4.0.RELEASE</p>
  
  <pre><code>This is my flow:
  ------------------
  
  Zuul -&gt; Service Discovery (Eureka Server) -&gt; Service
  </code></pre>
  
  <p>Kindly help, not sure where the Authorization header is vanishing. </p>
  
  <pre><code>Eureka Server yml file:
  -------------------------
  server.port:4001
  eureka.instance.hostname=localhost
  eureka.client.fetch-registry:false
  eureka.client.register-with-eureka:false
  eureka.client.serviceUrl.defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
  eureka.client.healthcheck.enabled=true
  
  Zuul yml file:
  -----------------
  server:
    port: 8765
  info:
    component: Edge Server
  eureka:
    instance:
      leaseRenewalIntervalInSeconds: 3
      metadataMap:
        instanceId: ${spring.application.name}:${random.value}
    client:
      # Default values comes from org.springframework.cloud.netflix.eurek.EurekaClientConfigBean
      registryFetchIntervalSeconds: 5
      instanceInfoReplicationIntervalSeconds: 5
      initialInstanceInfoReplicationIntervalSeconds: 5
  
  endpoints:
    restart:
      enabled: true
    shutdown:
      enabled: true
    health:
      sensitive: false
  
  zuul.sensitive-headers: Cookie,Set-Cookie,Authorization
  
  logging:
    level:
      ROOT: WARN
      se.callista: INFO
  
      # Get info regarding connection to the cofig server and retries if required
      org.springframework.cloud.config.client.ConfigServicePropertySourceLocator: INFO
      org.springframework.retry.support.RetryTemplate: DEBUG
  
      # Set INFO to see the allocated port
      org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer: INFO
  ---
  eureka:
    instance:
      preferIpAddress: true
    client:
      serviceUrl:
        defaultZone: http://localhost:4001/eureka,http://localhost:4002/eureka
  </code></pre>