Changes

testenv: stop daemons in reverse order

The PyHSS daemons throw a lot of errors when the redis server is stopped
before the PyHSS daemons are stopped. Fix this by stopping the daemons
in the reverse order they were started.

Example:

  start:
  	1) redis
  	2) pyhss_hss
  	3) pyhss_diameter
  	4) pyhss_api

  stop:
  	1) pyhss_api
  	2) pyhss_diameter
  	3) pyhss_hss
  	4) redis

Change-Id: Ia4fa25998d81a9a3a27c5f3d341b9a02e5536e17