Add an example on how to use 'contains' as condition
Add an example on how to use 'contains' as condition

This adds an example in docs on how to use
newly added function 'contains' as condition.

Change-Id: I9c5f314925f5b6592742cb4eb04e4c8247ec743c

noironetworks/heat,noironetworks/heat,openstack/heat,openstack/heat