autotest: balance_pools: use a RetryingAFE

BUG=chromium:840519
TEST=None

Change-Id: I90792352be334379326ae08deef297e9a3cd396b
Reviewed-on: https://chromium-review.googlesource.com/1048306
Commit-Ready: Aviv Keshet <akeshet@chromium.org>
Tested-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Richard Barnette <jrbarnette@google.com>
diff --git a/site_utils/balance_pools.py b/site_utils/balance_pools.py
index fb0298f..2078517 100755
--- a/site_utils/balance_pools.py
+++ b/site_utils/balance_pools.py
@@ -59,8 +59,8 @@
 
 import common
 from autotest_lib.server import constants
-from autotest_lib.server import frontend
 from autotest_lib.server import site_utils
+from autotest_lib.server.cros.dynamic_suite import frontend_wrappers
 from autotest_lib.server.lib import status_history
 from autotest_lib.site_utils import lab_inventory
 from autotest_lib.utils import labellib
@@ -642,7 +642,7 @@
         with metrics.SuccessCounter('chromeos/autotest/balance_pools/runs'):
             end_time = time.time()
             start_time = end_time - 24 * 60 * 60
-            afe = frontend.AFE(server=arguments.web)
+            afe = frontend_wrappers.RetryingAFE(server=arguments.web)
 
             def balancer(pool, labels):
                 """Balance the specified model.