One way to improve the performance of Ansible is through fact caching.
Rather than gather facts in every play, we can configure Ansible to
cache them in a persistent store. An example Ansible configuration for
doing this is as follows:

[defaults]
gathering = smart
fact_caching = jsonfile
fact_caching_connection = ./facts
fact_caching_timeout = 86400

This does not affect Kolla Ansible however, since we use the setup
module which unconditionally gathers facts regardless of the state of
the cache. This gets worse with large inventories limited to a small
batch of hosts via --limit or serial, since the limited hosts must
gather facts for all others.

One way to detect whether facts exist for a host is via the
'module_setup' variable, which exists only when facts exist. This change
uses the 'module_setup' fact to determine whether facts need to be
gathered for hosts outside of the batch. For hosts in the batch, we
switch from using the setup module to gather_facts on the play, which
can use the 'smart' gathering logic.

Change-Id: I04841fb62b2e1d9e97ce4b75ce3a7349b9c74036
Partially-Implements: blueprint performance-improvements

Prior to this change, when the --limit argument is used, each host in the
limit gathers facts for every other host. This is clearly unnecessary, and
can result in up to (N-1)^2 fact gathers.

This change gathers facts for each host only once. Hosts that are not in
the limit are divided between those that are in the limit, and facts are
gathered via delegation.

This change also factors out the fact gathering logic into a separate
playbook that is imported where necessary.

Change-Id: I923df5af41a7f1b7b0142d0da185a9a0979be543

In change I78cb60168aaa40bb6439198283546b7faf33917c, action was changed
to kolla_action, and serial to kolla_serial, to avoid Ansible warnings
due to use of reserved keywords. In that change, some keywords were
missed, and some changes that were merged since then have not switched
to the new variables. This change fixes all current instances of those
issues.

Change-Id: I357dffdfcb2b405e280a962d366ee65eebf0a8d1
Implements: blueprint migrate-to-ansible-2-2-0

This patchset implements yamllint test to all *.yml
files.

Also fixes syntax errors to make jobs to pass.

Change-Id: I3186adf9835b4d0cada272d156b17d1bc9c2b799

The ansible/kolla-host.yml playbook failed when called with a --limit
flag.

This was due to the fact that only the facts of the subset of hosts
were gathered but the "Generate /etc/hosts for all of the nodes" task
is using the ansible_<IFACE>.ipv4.address variable of all hosts.

The code for this fix is copied from the site.yml playbook
where it was used for the same reason.

Change-Id: I7e70caf750506ad8ab36ec024bd9647dd733fbd0
Closes-Bug: #1713725

Change-Id: I44c2668a8ebb6dd3201a6eb4e47284871380e6d7

Change-Id: Ie70db1b18a73528b1194e4fbcf53d09fed20f4a0
Implements: blueprint kolla-host