Add python-swift client to the requirements

Since Id4b27ee70f420f7536b4c698eb1f3bba15dbd1e8 we have swift scenarios tests
which means that we must include swiftclient as a requirement.
Closes-bug: #1265936

Change-Id: Iee233867446cce098dbce9e5ab9ab1d4b19d97b3
diff --git a/requirements.txt b/requirements.txt
index e070549..0c4a659 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -14,6 +14,7 @@
 python-neutronclient>=2.3.0,<3
 python-cinderclient>=1.0.6
 python-heatclient>=0.2.3
+python-swiftclient>=1.5
 testresources>=0.2.4
 keyring>=1.6.1,<2.0
 testrepository>=0.0.17