tests: Fix unversioned python shebang lines

- Unversioned python shebang lines may cause
  mixed python 2.7 and python 3 execution in
  make test.

Type: fix

Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
Change-Id: Ia82c37be33902718c48878378b8343eedb76c2c8

src/plugins/srv6-mobile/test/test_srv6_mobile.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 from framework import VppTestCase
 from ipaddress import IPv4Address

test/template_classifier.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import binascii
 import socket

test/test_srv6_un.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 from framework import VppTestCase
 from ipaddress import IPv4Address

test/vpp_teib.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """
   TEIB objects
 """