HostIlE - IE11 connects to a wrong host in cross domain scenarios whe…

…n a relative connection url is used (fixes SignalR#2959)

When parsing a relatinve uri with <a /> (anchor) IE11 does not provide the protocol so we fall back to using `window.document.location` to resolve connection details. However if the host could be read from the url provided by the user we should use it instead of the one from the `window.document.location`. The fix is to use the host from the url provided by the user if possible and fall back to using the host from the `window.document.location` if the host could not be read from the user's url.

src/Microsoft.AspNet.SignalR.Client.JS/jquery.signalR.core.js

@@ -485,14 +485,14 @@
             parser.href = connection.url;
             if (!parser.protocol || parser.protocol === ":") {
                 connection.protocol = window.document.location.protocol;
-                connection.host = window.document.location.host;
-                connection.baseUrl = connection.protocol + "//" + connection.host;
+                connection.host = parser.host || window.document.location.host;
             } else {
                 connection.protocol = parser.protocol;
                 connection.host = parser.host;
-                connection.baseUrl = parser.protocol + "//" + parser.host;
             }
 
+            connection.baseUrl = connection.protocol + "//" + connection.host;
+
             // Set the websocket protocol
             connection.wsProtocol = connection.protocol === "https:" ? "wss://" : "ws://";