Tweak logic for handling failed connections in lbry.jsonrpc_call()

- Move AJAX error callback declaration to the right spot (before,
   it was inside the load callback)
 - Add support for custom timeouts

js/lbry.js

@@ -10,8 +10,20 @@ var lbry = {
   }
 };
 
-lbry.jsonrpc_call = function (connectionString, method, params, callback, errorCallback, connectFailedCallback) {
+lbry.jsonrpc_call = function (connectionString, method, params, callback, errorCallback, connectFailedCallback, timeout) {
   var xhr = new XMLHttpRequest;
+  if (typeof connectFailedCallback !== 'undefined') {
+    if (timeout) {
+      xhr.timeout = timeout;
+    }
+
+    xhr.addEventListener('error', function (e) {
+      connectFailedCallback(e);
+    });
+    xhr.addEventListener('timeout', function() {
+      connectFailedCallback(new Error('XMLHttpRequest connection timed out'));
+    })
+  }
   xhr.addEventListener('load', function() {
     var response = JSON.parse(xhr.responseText);
 
@@ -24,12 +36,6 @@ lbry.jsonrpc_call = function (connectionString, method, params, callback, errorC
     }
   });
 
-  if (connectFailedCallback) {
-    xhr.addEventListener('error', function (e) {
-      connectFailedCallback(e);
-    });
-  }
-
   xhr.open('POST', connectionString, true);
   xhr.send(JSON.stringify({
     'jsonrpc': '2.0',