By default, docker containers inherit ulimit from limits of docker
deamon. On CentOS 7, docker daemon default NOFILE is 1048576.
It can found in /usr/lib/systemd/system/docker.service.
The big limit will cause many problem. we should control it in
production environment.

Change-Id: Iab962446a94ef092977728259d9818b86cfa7f68

Change index to ease identify what service want to look.
Split docs into more specific folder such as networking
and storage.

Change-Id: Ic7ac12b3dd555fa5c018eeb897ccd4a5a2dfe8f3

Following by https://review.openstack.org/#/c/605097/
These were used by now-dead tooling. We can remove them.

Change-Id: I0953751044f038a3fdd1acd49b3d2b053ac4bec8

This commit is to apply resource-constraints only to few OpenStack services.
Commit to apply constraints to other services will be made in coming commits.

Partially-Implements: blueprint resource-constraints

Change-Id: Icafa54baca24d2de64238222a5677b9d8b90e2aa

This commit will constrain the dimensions of service `Nova`
and sub-containers deployed along with it.

A user can give the dimension values in `/etc/kolla/globals.yml`
the data-types just like stated in this commit.

Reference-Docs:
https://docs.docker.com/config/containers/resource_constraints/

Added Test-cases for the same.

Partially-Implements: blueprint resource-constraints
Change-Id: I6458d8fb7b26a6e7c3a9fd0d674d9cf129b0bf5d