Wait for preview call to end in file list

When displaying the file list or scrolling down to formerly invisible
resources, wait for ajax calls to make sure the mediaSource and
preview loading call has ended before performing any operations.

This is to avoid running into file lock issues while loading the
previews.

tests/acceptance/helpers/loginHelper.js

@@ -20,7 +20,9 @@ module.exports = {
     }
     return client
       .page.phoenixPage()
+      .initAjaxCounters()
       .waitForElementVisible('@appContainer')
+      .waitForOutstandingAjaxCalls()
       .then(() => {
         client.globals.currentUser = userId
       })

tests/acceptance/helpers/navigationHelper.js

@@ -17,7 +17,9 @@ module.exports = {
       throw new Error('Invalid type for loading indicator selector')
     }
     return client
+      .initAjaxCounters()
       .waitForElementPresent({ ...locator, abortOnFailure: false }) // don't fail if we are too late
       .waitForElementNotPresent(locator)
+      .waitForOutstandingAjaxCalls()
   }
 }

tests/acceptance/pageObjects/FilesPageElement/filesList.js

@@ -199,13 +199,17 @@ module.exports = {
      */
     navigateToFolder: async function (folder) {
       await this.waitForFileVisible(folder)
+      await this.initAjaxCounters()
 
       await this.useXpath()
         .moveToElement(this.getFileRowSelectorByFileName(folder), 0, 0)
         .click(this.getFileLinkSelectorByFileName(folder))
         .useCss()
         .waitForElementNotPresent('@filesListProgressBar')
 
+      // wait for previews to finish loading
+      await this.waitForOutstandingAjaxCalls()
+
       return this
     },
     /**
@@ -540,6 +544,7 @@ module.exports = {
         itemName = this.replaceChar(itemName, '"', '\\"')
       }
 
+      await this.initAjaxCounters()
       await this.waitForElementVisible('@virtualScrollWrapper')
       await this.api.executeAsync(
         function (
@@ -588,6 +593,10 @@ module.exports = {
           listHeaderSelector: this.elements.filesTableHeader.selector
         }])
 
+      // wait for previews to be loaded after scrolling to resources that were
+      // not rendered before
+      await this.waitForOutstandingAjaxCalls()
+
       return this
     },