Bump oslo.config version

This commit just bumps the minimum version requirement for
oslo.config. Version 1.2.0 has been released so we should keep
tempest's required version in sync with the other projects.

Change-Id: Ie78070a9fe0759c30fb84ac892a257e0c5cbf246
diff --git a/requirements.txt b/requirements.txt
index b15fb92..3b9ec44 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -17,7 +17,7 @@
 testresources>=0.2.4
 keyring>=1.6.1
 testrepository>=0.0.17
-oslo.config>=1.1.0
+oslo.config>=1.2.0
 eventlet>=0.13.0
 six<1.4.0
 iso8601>=0.1.4