Remove sitepackages usage from testenv

Change-Id: Ibbe12f5e3baa88d96896f8fd903ba6e325b13874

tox.ini

@@ -2,7 +2,6 @@
 envlist = py26,py27,pep8
 
 [testenv]
-sitepackages = True
 setenv =
     VIRTUAL_ENV={envdir}
     NOSE_WITH_OPENSTACK=1
@@ -18,7 +17,6 @@ deps =
 commands = nosetests {posargs}
 
 [testenv:tests]
-sitepackages = False
 setenv =
     VIRTUAL_ENV={envdir}
     NOSE_WITH_OPENSTACK=1
@@ -34,11 +32,9 @@ commands = nosetests -w tests -x {posargs}
 setenv = NOSE_WITH_COVERAGE=1
 
 [tox:jenkins]
-sitepackages = False
 downloadcache = ~/cache/pip
 
 [testenv:pep8]
-sitepackages = False
 commands = flake8
 
 [testenv:venv]