Add nodepool integration test

This uses the python unittest framework to run a test similar to
the existing zuul-nodepool unit test, but expecting an actual
running nodepool.

Change-Id: I769e1421c146cc3545dce606487c8c72e3d3a4c5
diff --git a/tox.ini b/tox.ini
index 9c2daee..b7cbf27 100644
--- a/tox.ini
+++ b/tox.ini
@@ -44,6 +44,11 @@
 [testenv:validate-layout]
 commands = zuul-server -c etc/zuul.conf-sample -t -l {posargs}
 
+[testenv:nodepool]
+setenv =
+   OS_TEST_PATH = ./tests/nodepool
+commands = python setup.py testr --slowest --testr-args='--concurrency=1 {posargs}'
+
 [flake8]
 # These are ignored intentionally in openstack-infra projects;
 # please don't submit patches that solely correct them or enable them.