Retry the first login page validation

It can take longer that 60 seconds for the server to be ready to
respond. Retry the login page validation twice (i.e., 3 attempts
to validate the login page)

qa/qa/ce/strategy.rb

@@ -10,9 +10,18 @@ module QA
       end
 
       def perform_before_hooks
+        retries ||= 0
+
         # The login page could take some time to load the first time it is visited.
         # We visit the login page and wait for it to properly load only once before the tests.
         QA::Runtime::Browser.visit(:gitlab, QA::Page::Main::Login)
+      rescue QA::Page::Validatable::PageValidationError
+        if (retries += 1) < 3
+          Runtime::Logger.warn("The login page did not appear as expected. Retrying... (attempt ##{retries})")
+          retry
+        end
+
+        raise
       end
     end
   end