Multi-Node Lab in DevStack incorrect nova-manage path

[Mario Kostadincev]

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:

- [ ] This doc is inaccurate in this way: ______
- [ ] This is a doc addition request.
- [x] I have a fix to the document that I can paste below including example: input and output.
current: for i in `seq 2 10`; do /opt/stack/nova/bin/nova-manage fixed reserve 10.4.128.$i; done
should be: for i in `seq 2 10`; do /usr/local/bin/nova-manage fixed reserve 10.4.128.$i; done

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-----------------------------------
Release: on 2018-07-12 11:39
SHA: 3b5477d6356a62d7d64a519a4b1ac99309d251c0
Source: https://git.openstack.org/cgit/openstack-dev/devstack/tree/doc/source/guides/multinode-lab.rst
URL: https://docs.openstack.org/devstack/latest/guides/multinode-lab.html

[Dr. Jens Harbott (j-harbott)]

Actually this command only made sense when running nova-network instead of Neutron, which isn't an option anymore. I'll do a test-run of the complete lab before putting up a patch.