Adds unitest2 and keyring to pip-requires

When running tempest outside of a devstack
machine, the unittest2 and keyring packages
are missing from the virtual environment.

Adding the packages to tools/pip-requires
triggers their installation both when
using run_tests.sh as well as tox.

Fixes: LP bug #1112542
Change-Id: I5c3632394a2b0fe364022854d8ff62ef4866ace9
diff --git a/tools/pip-requires b/tools/pip-requires
index dcc859f..504ca24 100644
--- a/tools/pip-requires
+++ b/tools/pip-requires
@@ -11,3 +11,5 @@
 python-novaclient>=2.10.0
 python-quantumclient>=2.1
 testresources
+unittest2
+keyring