standardize on -1 for default timeouts
diff --git a/src/python/oftest/ofutils.py b/src/python/oftest/ofutils.py
index 9e59c5d..3fd9df9 100644
--- a/src/python/oftest/ofutils.py
+++ b/src/python/oftest/ofutils.py
@@ -12,18 +12,23 @@
 """
 Wait on a condition variable until the given function returns non-None or a timeout expires.
 The condition variable must already be acquired.
+The timeout value -1 means use the default timeout.
 There is deliberately no support for an infinite timeout.
 TODO: get the default timeout from configuration
 """
-def timed_wait(cv, fn, timeout=10):
+def timed_wait(cv, fn, timeout=-1):
+    if timeout == -1:
+        # TODO make this configurable
+        timeout = 5
+
     end_time = time.time() + timeout
     while True:
-        if time.time() > end_time:
-            return None
-
         val = fn()
         if val != None:
             return val
 
         remaining_time = end_time - time.time()
         cv.wait(remaining_time)
+
+        if time.time() > end_time:
+            return None