As it stands now, it is difficult to write idempotent tasks for digital
ocean droplets.  Digital ocean assigns new nodes a random id when they
are provisioned and that id is the only key that can be used to identify
it in subsequent runs of that play.

The workflow previously involved manual intervention:

- write a play defining a new node with no specified id
- run it, collect the randomly assigned id by hand
- modify the play to add the id by hand so future runs don't create
  duplicate nodes
- perform future re-runs that check if the node exists (by its id)
  - if it does exist then do nothing.
  - if it does not exist, then create it and return a *new random id*
  - collect the new random id by hand, modify the playbook file, and
    start all over.

Its a huge pain.

The modifications in this commit allow you to use the 'hostname' as a
primary key for idempotence with digital ocean.  By default, digital
ocean will let you create as many hosts with the same hostname as you
like.  Here, we provide an option to constrain the user to using only
unique hostnames.

The workflow will now look like:

- write a play defining a new node with a specified hostname and
  "unique_name: true""
- run it, create the new node and move on.
- re-run it, notice that a node with that hostname is already created
  and move on.

Merge branch 'fix/apt_repository_update_cache' of https://github.com/resmo/ansible into resmo-fix/apt_repository_update_cache

The default behavior is to update_cache if changed.

If you add more then one repo, you may not want to update cache for every repo separately.
So you can now disable update_cache with this new option e.g. update_cache=no

Updating cache can also be handled using the apt module.

Cosmetic - Digital ocean cleanup

The EXAMPLES block here has two copies of the same docs,
one nicely formatted, the other less so.

It looks like a pass was made to clean up the docs but the old
cruftier ones were never removed.

zabbix inventory: print errors to stderr

Two fixes:

* parameter name is selevel, not serange.
* Fix split on selinux context to limit to max of 4 since the selevel
  may contain ':' characters.  This was fixed in
  selinux_default_context() and selinux_context().

apt: fixed duplicate fail_json

Fixed monit restarted error.

Errors everytime...

Conflicts:
	lib/ansible/playbook/play.py

Previously, includes had to receive variables via a special 'vars'
field. With this patch, the include syntax becomes a more natural
datastructure without special fields and is more akin to the way
role includes/dependencies work.

Tested with the following playbook:
---
- hosts: localhost
  connection: local
  tasks:
  - { include: inc1.yml, a: 1 }
  - include: inc2.yml
    b: 2
  - include: inc3.yml
    with_items:
    - x
    - y
    - z

Fixes #3481

Fixes #4129

Merge branch 'subelements' of https://github.com/sergevanginderachter/ansible into sergevanginderachter-subelements

Conflicts:
	lib/ansible/runner/connection_plugins/accelerate.py

Fixes #4111

- use egrep patterns to detect BSDs in one ifeq
- use seconds-since-epoch as input for BSD date (-r option)
- get seconds-since-epoch from git log with "%at" format string

Add some more OpenBSD facts

Expand tilde in paths in file module