Pin python-novaclient<=6.0.0

[lpramuk]

• avoid installing python-novaclient 7.0+

  Traceback (most recent call last):
  File "./5minute.py", line 6, in <module>
  main(sys.argv[1:])
  File "/home/lpramuk/git/SatelliteQE/5minute/vminute/vminute.py", line 1435, in main
  ListInstancesClass().cmd(argv)
  File "/home/lpramuk/git/SatelliteQE/5minute/vminute/vminute.py", line 613, in cmd
  self.list_instances(filter)
  File "/home/lpramuk/git/SatelliteQE/5minute/vminute/vminute.py", line 170, in wrapper
  raise ex
  keystoneauth1.exceptions.http.Unauthorized: The request you have made requires authentication. (HTTP 401) (Request-ID: req-d822744e-7cba-4e14-a80d-258d6bc9b027)