[JENKINS-39741] - Redirect to login page after authorisation error wh…

…en checking connectivity to update center and handle any other error.

war/src/main/js/util/jenkins.js

@@ -244,7 +244,14 @@ exports.testConnectivity = function(siteId, handler) {
 					handler(true);
 				}
 			}
-		});
+		}, { error: function(xhr, textStatus, errorThrown) {
+                 if (xhr.status === 403) {
+                     exports.goTo('/login');
+                 } else {
+                     handler.call({ isError: true, errorMessage: errorThrown });
+                 }
+               }
+             });
 	};
 	testConnectivity();
 };