[intfstat] fix variable name (sonic-net#466)

Author: mykolaf

scripts/intfstat

@@ -338,7 +338,7 @@ def main():
         print "The rates are calculated within %s seconds period" % wait_time_in_seconds
         cnstat_new_dict = intfstat.get_cnstat(rif=interface_name)
         if interface_name:
-            intfstat.cnstat_single_interface(interface_name, cnstat_dict, cnstat_cached_dict)
+            intfstat.cnstat_single_interface(interface_name, cnstat_new_dict, cnstat_dict)
         else:
             intfstat.cnstat_diff_print(cnstat_new_dict, cnstat_dict, use_json)
 

sonic-utilities-tests/intfstat_test.py

@@ -47,6 +47,12 @@ def test_period(self):
         print(result.output)
         assert result.output.split('\n')[0] == "The rates are calculated within 3 seconds period"
 
+    def test_period_single_interface(self):
+        runner = CliRunner()
+        result = runner.invoke(show.cli.commands["interfaces"].commands["counters"].commands["rif"], ["Ethernet20", "-p3"])
+        print(result.output)
+        assert result.output.split('\n')[0] == "The rates are calculated within 3 seconds period"
+
     def test_single_intfs(self):
         runner = CliRunner()
         result = runner.invoke(show.cli.commands["interfaces"].commands["counters"].commands["rif"], ["Ethernet20"])