CASSJAVA-55 Remove setting "Host" header for metadata requests.

With some sysprops enabled this will actually be respected which completely borks Astra routing.

patch by Bret McGuire; reviewed by Alexandre Dutra and Bret McGuire for CASSJAVA-55

driver-core/src/main/java/com/datastax/driver/core/CloudConfigFactory.java

@@ -208,7 +208,6 @@ protected BufferedReader fetchProxyMetadata(URL metadataServiceUrl, SSLContext s
     HttpsURLConnection connection = (HttpsURLConnection) metadataServiceUrl.openConnection();
     connection.setSSLSocketFactory(sslContext.getSocketFactory());
     connection.setRequestMethod("GET");
-    connection.setRequestProperty("host", "localhost");
     return new BufferedReader(new InputStreamReader(connection.getInputStream(), UTF_8));
   }