faft: Fix the missing retry loop for launching client

Add the missing retry loop back; otherwise, only launch client once.

BUG=chrome-os-partner:16037
TEST=run a FAFT test and pass.

Change-Id: I9ce31e43311b5707350576da2de8eec06e2ae948
Reviewed-on: https://gerrit.chromium.org/gerrit/39156
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
diff --git a/server/cros/servo_test.py b/server/cros/servo_test.py
index 82f6bb7..4ee62ca 100644
--- a/server/cros/servo_test.py
+++ b/server/cros/servo_test.py
@@ -185,15 +185,17 @@
           info: A dict of remote info, see the definition of self._remote_infos.
         """
         retry = 3
-        try:
-            self._launch_client_once(info)
-        except AssertionError:
-            if retry:
+        while retry:
+            try:
+                self._launch_client_once(info)
+                break
+            except AssertionError:
                 retry -= 1
-                logging.info('Retry again...')
-                time.sleep(5)
-            else:
-                raise
+                if retry:
+                    logging.info('Retry again...')
+                    time.sleep(5)
+                else:
+                    raise
 
 
     def _launch_client_once(self, info):