We filter all resources for overcloud root stack with a
non-indexed field 'physical_resource_id' (nova_instance).
This is very inefficient.
With this patch, though there would still be making heat api
calls for every deployment, it won't be so expensive.
Change-Id: I260501e6061c0d6652b22504e7284940b2c64709
Closes-Bug: #1838861
(cherry picked from commit 3df3719e82)