add the version requirement for testtools

when I run tempest, it display:
 'module' object has no attribute 'WithAttributes'.
But I have install testtools. when I upgrade testtools, the problem
is resovled. So I think we should require the version of testtools
in pip-requires.

Fixes bug 1133177

Change-Id: Ib30fa31f1a412981263bf93bc37c5f1d3918cf1f
diff --git a/tools/pip-requires b/tools/pip-requires
index 5c45a49..220f1a6 100644
--- a/tools/pip-requires
+++ b/tools/pip-requires
@@ -1,7 +1,7 @@
 anyjson
 nose
 httplib2>=0.7.0
-testtools
+testtools>=0.9.29
 lxml
 boto>=2.2.1
 paramiko