zdtm.py: Fix eval error if empty desc file provided

If desc is empty we should not try to eval it,
otherwise it would lead to exceptio. So test
for its size as well.

travis-ci: success for zdtm.py: Fix eval error if empty desc file provided
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm.py

@@ -1464,7 +1464,7 @@ default_test = {}
 
 def get_test_desc(tname):
 	d_path = tname + '.desc'
-	if os.access(d_path, os.F_OK):
+	if os.access(d_path, os.F_OK) and os.path.getsize(d_path) > 0:
 		return eval(open(d_path).read())
 
 	return default_test