SEBA-752 fixing atests in voltha-1.7

Change-Id: Id99a24a72e35baa31096750bf7fb12424017124f
diff --git a/tests/atests/common/unicast.py b/tests/atests/common/unicast.py
index 69d3d1a..1622b99 100644
--- a/tests/atests/common/unicast.py
+++ b/tests/atests/common/unicast.py
@@ -78,7 +78,7 @@
     def execute_tcpdump(self):
         logging.info('Execute tcpdump')
         process_output = open('%s/%s' % (testCaseUtils.get_dir(self, 'log'), self.TCPDUMP_FILENAME), 'w')
-        tcpdump = subprocess.Popen(['sudo', '/usr/sbin/tcpdump', '-nei', 'pon1'],
+        tcpdump = subprocess.Popen(['sudo', '/usr/sbin/tcpdump', '-nei', 'nni0'],
                                    stdout=process_output,
                                    stderr=process_output)
         self.__tcpdumpPid = tcpdump.pid