fix(integration): wait for login modal to close before clicking UI elements

The Selenium test InterpreterModeActionsIT.testPerUserIsolatedAction
fails intermittently because the login modal overlay remains visible
after authentication, causing ElementClickInterceptedException when
the test tries to click the user dropdown button.

Wait for the modal to become invisible and remove any lingering
backdrop via JavaScript before proceeding.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: jongyoul

zeppelin-integration/src/test/java/org/apache/zeppelin/AbstractZeppelinIT.java

@@ -61,7 +61,19 @@ protected void authenticationUser(String userName, String password) {
         By.xpath("//*[@id='loginModalContent']//button[contains(.,'Login')]"),
         MAX_BROWSER_TIMEOUT_SEC).click();
 
-    ZeppelinITUtils.sleep(1000, false);
+    // Wait for the login modal to fully close before interacting with other elements
+    WebDriverWait wait = new WebDriverWait(manager.getWebDriver(),
+        Duration.ofSeconds(MAX_BROWSER_TIMEOUT_SEC));
+    wait.until(ExpectedConditions.invisibilityOfElementLocated(By.id("loginModal")));
+
+    // Dismiss any lingering modal backdrop via JavaScript
+    try {
+      ((JavascriptExecutor) manager.getWebDriver()).executeScript(
+          "document.querySelectorAll('.modal-backdrop').forEach(e => e.remove());");
+    } catch (Exception e) {
+      // ignore if not ready
+    }
+    ZeppelinITUtils.sleep(500, false);
   }
 
   protected void logoutUser(String userName) throws URISyntaxException {