stats: check epoch in python vpp_stats ls

The VPP Stats Python binding was missing checking epoch.
Resulting it would not pick up changes in the directory.

Type: fix
Signed-off-by: Ole Troan <ot@cisco.com>
Change-Id: I3226d71c77be2e80e24b5cd48fc9820833f7d30e
Signed-off-by: Ole Troan <ot@cisco.com>
diff --git a/src/vpp-api/python/vpp_papi/vpp_stats.py b/src/vpp-api/python/vpp_papi/vpp_stats.py
index b9b23b5..3831a82 100755
--- a/src/vpp-api/python/vpp_papi/vpp_stats.py
+++ b/src/vpp-api/python/vpp_papi/vpp_stats.py
@@ -280,6 +280,9 @@
         if not isinstance(patterns, list):
             patterns = [patterns]
         regex = [re.compile(i) for i in patterns]
+        if self.last_epoch != self.epoch:
+            self.refresh()
+
         return [k for k, v in self.directory.items()
                 if any(re.match(pattern, k) for pattern in regex)]