This patch introduces a ports pool manager that runs as an http server
thread belonging to the VIF handler. This Manager handles the requests
to populate and/or empty given subport pools so that they can be easily
managed.
It also includes a client and documentation to test/use the new functionality.
Implements: blueprint kuryr-manager-cli-tool
Change-Id: I495c0ca3ed997ab9da1763d8a3e60bbf7ac618b9