Add workaround to support tox 1.7.2

Conflicts:
	tox.ini

Change-Id: I58542f6e7dbbad98517c09b6176b9827f66dd1ff
Partial-Bug: 1348818
(cherry picked from commit 61b44eaceb)

tox.ini

@@ -13,6 +13,9 @@ setenv = VIRTUAL_ENV={envdir}
          NOSE_OPENSTACK_YELLOW=0.025
          NOSE_OPENSTACK_SHOW_ELAPSED=1
          NOSE_OPENSTACK_STDOUT=1
+         # FIXME(dolph): overriding the hash seed with a constant is a
+         # workaround for bug 1348818
+         PYTHONHASHSEED=0
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = python tools/patch_tox_venv.py