Filter out test directory which has only control files.

src/scripts/autotest

Index: src/scripts/autotest
diff --git a/src/scripts/autotest b/src/scripts/autotest
index 28b025b7e2b40e6f3fb96ec33f49ffd51c0ec6e6..7877dd2be5668128041897340246420e9258774d 100755
--- a/src/scripts/autotest
+++ b/src/scripts/autotest
@@ -150,8 +150,10 @@ def build_autotest(options):
   site_tests = '../third_party/autotest/files/client/site_tests'
   for site_test in os.listdir(site_tests):
     test_path = os.path.join(site_tests, site_test)
-    if (os.path.exists(test_path) and os.path.isdir(test_path)
-        and site_test not in blacklist):
+    test_py = os.path.join(test_path, '%s.py' % site_test)
+    if (os.path.exists(test_path) and os.path.isdir(test_path) and
+        os.path.exists(test_py) and os.path.isfile(test_py) and
+        site_test not in blacklist):
       all_tests += ',' + site_test
 
   if 'all' == options.build.lower():