[contrail] typo in the vsrx test helper

Detailed bug description:
 Regression test for contrail5.0 is blocked by the "SyntaxError: invalid syntax"
Steps to reproduce:
 Run contrail_bvt testgroup
Expected results:
 Test should be started
Actual result:
 CI test was has been failed with the error: "SyntaxError: invalid syntax"
Reproducibility:
 100%
Impact:
 CI
Description of the environment:
 n/a
Additional information:

Traceback (most recent call last):
  File "/home/jenkins/workspace/9.1.contrail.5.0.bvt.test.juniper/plugin_test/run_tests.py", line 78, in <module>
    import_tests()
  File "/home/jenkins/workspace/9.1.contrail.5.0.bvt.test.juniper/plugin_test/run_tests.py", line 54, in import_tests
    from tests import test_smoke_bvt # noqa
  File "/home/jenkins/workspace/9.1.contrail.5.0.bvt.test.juniper/plugin_test/tests/test_smoke_bvt.py", line 30, in <module>
    from helpers import vsrx
  File "/home/jenkins/workspace/9.1.contrail.5.0.bvt.test.juniper/plugin_test/helpers/vsrx.py", line 103
    for i in range(10)
                      ^
SyntaxError: invalid syntax