Add branch coverage reporting

Except where the python-nose package version does not support the
"--cover-branches" option.

Change-Id: I9ea6452d9834b3ac414e14e628002f593dd4b8c8
Signed-off-by: Peter Portante <peter.portante@redhat.com>

tox.ini

@@ -9,6 +9,8 @@ setenv = VIRTUAL_ENV={envdir}
          NOSE_OPENSTACK_YELLOW=0.025
          NOSE_OPENSTACK_SHOW_ELAPSED=1
          NOSE_OPENSTACK_STDOUT=1
+         NOSE_WITH_COVERAGE=1
+         NOSE_COVER_BRANCHES=1
 deps =
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
@@ -22,9 +24,6 @@ commands =
   flake8
   flake8 --filename=swift* bin
 
-[testenv:cover]
-setenv = NOSE_WITH_COVERAGE=1
-
 [testenv:venv]
 commands = {posargs}