Add release notes page for 17.1.0 & 17.2.0

This commit adds new index pages for 17.1.0 and 17.2.0
releases.

Currently there is no index page for 17.1.0
and 17.2.0 on release notes page
- https://docs.openstack.org/releasenotes/tempest/

Change-Id: If405d16b77171ebaabc39547a75c6da3b4234197
diff --git a/releasenotes/source/index.rst b/releasenotes/source/index.rst
index d968a44..d301f9c 100644
--- a/releasenotes/source/index.rst
+++ b/releasenotes/source/index.rst
@@ -7,6 +7,8 @@
 
     unreleased
     v18.0.0
+    v17.2.0
+    v17.1.0
     v17.0.0
     v16.1.0
     v16.0.0