Stabilize functional tests

Author: ishakhsuvarov

app/code/Magento/Checkout/Test/Mftf/ActionGroup/AssertMiniCartEmptyActionGroup.xml

@@ -13,6 +13,7 @@
             <description>Validates that the provided Product Count appears in the Storefront Header next to the Shopping Cart icon. Clicks on the Mini Shopping Cart icon. Validates that the 'No Items' message is present and correct in the Storefront Mini Shopping Cart.</description>
         </annotations>
 
+        <wait stepKey="waitForMinicartAjaxCallToComplete" time="15"/>
         <dontSeeElement selector="{{StorefrontMinicartSection.productCount}}" stepKey="dontSeeMinicartProductCount"/>
         <click selector="{{StorefrontMinicartSection.showCart}}" stepKey="expandMinicart"/>
         <see selector="{{StorefrontMinicartSection.minicartContent}}" userInput="You have no items in your shopping cart." stepKey="seeEmptyCartMessage"/>