Remove PYTHONHASHSEED=0 from tox.ini

We've ironed out remaining issues that crop up when running
with a random seed. This updates tox.ini to revert to the default
behavior of running with PYTHONHASHSEED=random.  The pep8 check
continues to run with PYTHONHASHSEED=0 to workaround oslo issues
around config value ordering in the check_uptodate.sh test.

Change-Id: Ifa0dba8c3970fc676d374f33c129ef0f9d526c94

tox.ini

@@ -6,28 +6,23 @@ skipsdist = True
 [testenv]
 setenv = VIRTUAL_ENV={envdir}
          OS_TEST_PATH=./tempest/test_discover
-         PYTHONHASHSEED=0
 usedevelop = True
 install_command = pip install -U {opts} {packages}
 
 [testenv:py26]
 setenv = OS_TEST_PATH=./tempest/tests
-         PYTHONHASHSEED=0
 commands = python setup.py test --slowest --testr-arg='tempest\.tests {posargs}'
 
 [testenv:py33]
 setenv = OS_TEST_PATH=./tempest/tests
-         PYTHONHASHSEED=0
 commands = python setup.py test --slowest --testr-arg='tempest\.tests {posargs}'
 
 [testenv:py27]
 setenv = OS_TEST_PATH=./tempest/tests
-         PYTHONHASHSEED=0
 commands = python setup.py test --slowest --testr-arg='tempest\.tests {posargs}'
 
 [testenv:cover]
 setenv = OS_TEST_PATH=./tempest/tests
-         PYTHONHASHSEED=0
 commands = python setup.py testr --coverage --testr-arg='tempest\.tests {posargs}'
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
@@ -96,6 +91,7 @@ deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 
 [testenv:pep8]
+setenv = PYTHONHASHSEED=0
 commands =
    flake8 {posargs}
    {toxinidir}/tools/config/check_uptodate.sh