CA-383987: Only include valid Hosts and Ports in tracing Host header

Signed-off-by: Steven Woods <steven.woods@citrix.com>

ocaml/libs/tracing/tracing.ml

@@ -688,16 +688,26 @@ module Export = struct
       let export ~url json =
         try
           let body = json in
-          (*If host or port is None it will throw a more meaningful error later, so ignore here*)
-          let hostname = match Uri.host url with Some h -> h | None -> "" in
-          let port = match Uri.port url with Some p -> p | None -> 80 in
           let headers =
             Cohttp.Header.of_list
-              [
-                ("Content-Type", "application/json")
-              ; ("Content-Length", string_of_int (String.length body))
-              ; ("Host", hostname ^ ":" ^ string_of_int port)
-              ]
+              ([
+                 ("Content-Type", "application/json")
+               ; ("Content-Length", string_of_int (String.length body))
+               ]
+              @
+              match Uri.host url with
+              | None ->
+                  []
+              | Some h ->
+                  let port =
+                    match Uri.port url with
+                    | Some p ->
+                        ":" ^ string_of_int p
+                    | None ->
+                        ""
+                  in
+                  [("Host", h ^ port)]
+              )
           in
           Open_uri.with_open_uri url (fun fd ->
               let request =