fix(tests): prefix with toxinidir variable with a / to ensure path to ensure-zookeeper-env.sh is correct

Author: StephenSorriaux

tox.ini

@@ -37,7 +37,7 @@ deps =
     sasl: kerberos
 commands =
     sasl: {toxinidir}/init_krb5.sh {envtmpdir}/kerberos \
-    {toxinidir}/ensure-zookeeper-env.sh \
+        /{toxinidir}/ensure-zookeeper-env.sh \
         nosetests {posargs: -d -v --with-coverage kazoo.tests}
 
 [flake8]