Install the Container Infrastructure Management service from source in magnum

[Ed Balduf]

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [x] This doc is inaccurate in this way: Step 5: policy.json file does not exist. There is a magnum-policy-generator.conf file which can be used to build a policy.yaml file. Not sure yet if this will work without other mods but for now this is a problem.

- [ ] This is a doc addition request.
- [ ] I have a fix to the document that I can paste below including example: input and output.

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-----------------------------------
Release: 5.0.2.dev14 on 2017-11-29 17:06
SHA: c58b727bec3561d8d283497d784a3437185924dd
Source: https://git.openstack.org/cgit/openstack/magnum/tree/doc/source/install/install-guide-from-source.rst
URL: https://docs.openstack.org/magnum/pike/install/install-guide-from-source.html