Support for addition of compute node into the running environment

Summary
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- To provide the support for adding new compute node through templates.

Motivation
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- While working on multi-node network, when we need more computation power, it is difficult to add compute node. Always we have to do it manually. So we wish to provide a mechanism so that we can do it through templates that we can run from controller without manual intervention of the user.

Description
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- A new feature will be added in horizon which will allow to add a new compute node through templates from controller.