Restore some loader.waitOnClosed() calls (#11348)

Signed-off-by: Thomas Mäder <[email protected]>

selenium/che-selenium-test/src/main/java/org/eclipse/che/selenium/pageobject/ProjectExplorer.java

@@ -291,6 +291,8 @@ public void waitItem(String path) {
    * @param timeout waiting timeout in seconds
    */
   public void waitItem(String path, int timeout) {
+    loader.waitOnClosed();
+
     seleniumWebDriverHelper.waitVisibility(
         By.xpath(format(PROJECT_EXPLORER_ITEM_TEMPLATE, path)), timeout);
   }
@@ -301,6 +303,8 @@ public void waitItem(String path, int timeout) {
    * @param reference git reference e.g. branch, tag or commit
    */
   public void waitReferenceName(String reference) {
+    loader.waitOnClosed();
+
     seleniumWebDriverHelper.waitTextEqualsTo(projectReference, "(" + reference + ")");
   }
 
@@ -440,6 +444,8 @@ public List<WebElement> waitVisibilitySeveralItemsByName(String... names) {
    * @return found {@link WebElement}
    */
   public WebElement waitVisibilityByName(String name, int timeOut) {
+    loader.waitOnClosed();
+
     return seleniumWebDriverHelper.waitVisibility(
         By.xpath(format("//div[@id='gwt-debug-projectTree']//div[text()='%s']", name)), timeOut);
   }
@@ -610,6 +616,7 @@ public void waitDisappearItemByPath(String path) {
    * @param folderType folder's type, defined in {@link FolderTypes}
    */
   public void waitDefinedTypeOfFolder(String path, FolderTypes folderType) {
+    loader.waitOnClosed();
     seleniumWebDriverHelper.waitVisibility(
         By.xpath(
             format(