Fixes example in the mapping combinations docs
Fixes example in the mapping combinations docs

When reviewing If74aaf07b77399f1648843280153c7523de5eb38 I noticed that
one of the examples was incorrect.

Change-Id: I4d5d88ea45c00fe874382c06a0626ea6aaeb87c9
Related-Bug: #1575057

ilay09/keystone,mahak/keystone,rajalokan/keystone,cernops/keystone,mahak/keystone,openstack/keystone,ilay09/keystone,rajalokan/keystone,openstack/keystone,openstack/keystone,mahak/keystone,ilay09/keystone,cernops/keystone,rajalokan/keystone