always use sitepackages

we really don't need to be compiling lxml at 3.5 when 2.3 is good
enough. So specify that we can always use sitepackages, as well
as don't pip -U, so we use requirements as intended.

Change-Id: If9f337d6bb688d46ab68dc1276e0f499a7dec8fd
diff --git a/tox.ini b/tox.ini
index b44b3e0..6d596e3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,13 +4,14 @@
 skipsdist = True
 
 [testenv]
+sitepackages = True
 setenv = VIRTUAL_ENV={envdir}
          LANG=en_US.UTF-8
          LANGUAGE=en_US:en
          LC_ALL=C
          OS_TEST_PATH=./tempest/test_discover
 usedevelop = True
-install_command = pip install -U {opts} {packages}
+install_command = pip install {opts} {packages}
 
 [testenv:py26]
 setenv = OS_TEST_PATH=./tempest/tests
@@ -25,38 +26,32 @@
 commands = python setup.py test --slowest --testr-arg='tempest\.tests {posargs}'
 
 [testenv:all]
-sitepackages = True
 setenv = VIRTUAL_ENV={envdir}
 commands =
   python setup.py testr --slowest --testr-args='{posargs}'
 
 [testenv:full]
-sitepackages = True
 # The regex below is used to select which tests to run and exclude the slow tag:
 # See the testrepostiory bug: https://bugs.launchpad.net/testrepository/+bug/1208610
 commands =
   bash tools/pretty_tox.sh '(?!.*\[.*\bslow\b.*\])(^tempest\.(api|scenario|thirdparty|cli)) {posargs}'
 
 [testenv:testr-full]
-sitepackages = True
 commands =
   bash tools/pretty_tox.sh '(?!.*\[.*\bslow\b.*\])(^tempest\.(api|scenario|thirdparty|cli)) {posargs}'
 
 [testenv:heat-slow]
-sitepackages = True
 setenv = OS_TEST_TIMEOUT=1200
 # The regex below is used to select heat api/scenario tests tagged as slow.
 commands =
   bash tools/pretty_tox_serial.sh '(?=.*\[.*\bslow\b.*\])(^tempest\.(api|scenario)\.orchestration) {posargs}'
 
 [testenv:large-ops]
-sitepackages = True
 commands =
   python setup.py testr --slowest --testr-args='tempest.scenario.test_large_ops {posargs}'
 
 
 [testenv:py26-full]
-sitepackages = True
 setenv = VIRTUAL_ENV={envdir}
          NOSE_WITH_OPENSTACK=1
          NOSE_OPENSTACK_COLOR=1
@@ -81,12 +76,10 @@
   nosetests --logging-format '%(asctime)-15s %(message)s' --with-xunit -sv --attr=type=smoke --xunit-file=nosetests-smoke.xml tempest {posargs}
 
 [testenv:smoke]
-sitepackages = True
 commands =
    bash tools/pretty_tox.sh '(?!.*\[.*\bslow\b.*\])((smoke)|(^tempest\.scenario)) {posargs}'
 
 [testenv:smoke-serial]
-sitepackages = True
 # This is still serial because neutron doesn't work with parallel. See:
 # https://bugs.launchpad.net/tempest/+bug/1216076 so the neutron smoke
 # job would fail if we moved it to parallel.
@@ -94,7 +87,6 @@
    bash tools/pretty_tox_serial.sh '(?!.*\[.*\bslow\b.*\])((smoke)|(^tempest\.scenario)) {posargs}'
 
 [testenv:stress]
-sitepackages = True
 commands =
     python -m tempest/stress/run_stress -a -d 3600 -S