Let the cover venv run individual tests.

Also, delete cruft from tox.ini while we're in there.

Change-Id: I8fe43695bb25b9c5eec10711b12d2002f1237e52

tox.ini

@@ -3,12 +3,6 @@ envlist = py26,py27,pep8
 
 [testenv]
 setenv = VIRTUAL_ENV={envdir}
-         NOSE_WITH_OPENSTACK=1
-         NOSE_OPENSTACK_COLOR=1
-         NOSE_OPENSTACK_RED=0.05
-         NOSE_OPENSTACK_YELLOW=0.025
-         NOSE_OPENSTACK_SHOW_ELAPSED=1
-         NOSE_OPENSTACK_STDOUT=1
 deps = -r{toxinidir}/tools/pip-requires
        -r{toxinidir}/tools/test-requires
        setuptools_git>=0.4
@@ -28,11 +22,9 @@ commands =
 commands = python ./tools/check_i18n.py ./quantum ./tools/i18n_cfg.py
 
 [testenv:cover]
-# Also do not run test_coverage_ext tests while gathering coverage as those
-# tests conflict with coverage.
-setenv = VIRTUAL_ENV={envdir}
 commands =
-  python setup.py testr --coverage
+  python tools/patch_tox_venv.py
+  python setup.py testr --coverage --testr-args='{posargs}'
 
 [testenv:venv]
 commands = {posargs}