usedevelop in tox

We want to run code inside of the venv, not outside.

Change-Id: I92c5e35674933ac4d9d15eda32f3b9339dbedbd3

tox.ini

@@ -1,12 +1,15 @@
 [tox]
+minversion = 1.6
+skipsdist = True
 envlist = py26,py27,py33,pep8
 
 [testenv]
-sitepackages = False
 setenv = VIRTUAL_ENV={envdir}
          LANG=en_US.UTF-8
          LANGUAGE=en_US:en
          LC_ALL=C
+usedevelop = True
+install_command = pip install {opts} {packages}
 
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
@@ -16,11 +19,9 @@ commands =
   {toxinidir}/tools/conf/check_uptodate.sh
 
 [tox:jenkins]
-sitepackages = True
 downloadcache = ~/cache/pip
 
 [testenv:pep8]
-sitepackages = False
 commands =
   flake8 {posargs} . cinder/common
   flake8 --filename=cinder* bin