Description of problem:

The OSP13 Ceph documentation should warn about the problems
of using name-based methods of referring to block devices and
suggests use of the by_path method to avoid this problem. 
The bz#1796191 contains a new utility to solve this issue and
we need to describe how to use it to the end users.
Here [1] the upstream related documentation.

[1] https://docs.openstack.org/project-deploy-guide/tripleo-docs/latest/features/node_specific_hieradata.html#generating-the-heat-environment-file-for-ceph-devices


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