Remove dependency on keyring

I don't see this used anywhere, so lets drop the
dependency.

Change-Id: Icf14648ad7e82a05d942f53fe38e9757aece691c
diff --git a/requirements.txt b/requirements.txt
index 75a61e7..2f28aae 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -17,7 +17,6 @@
 python-saharaclient>=0.6.0
 python-swiftclient>=2.0.2
 testresources>=0.2.4
-keyring>=2.1
 testrepository>=0.0.18
 oslo.config>=1.2.0
 six>=1.6.0