add strategy mitogen_linear when installed mitogen (#5985)

* add strategy mitogen_linear when installed mitogen

* add small docs

Rename playbook file

The raw action executes as a regular Mitogen connection, which requires Python on the target, so add strategy: linear to bootstrap-os role playbook.

* add mitogen to  CI test
fix typo

* enable mitogen test on deploy-part1 tests
change version from master to release
download tar.gz archive

* run all CI tests with mitogen

* disable mitogen with upgrade CI tests

* enable mitogen on CI tests via env vars

* disable mitogen on CI test by default, enable on some different OS

* disable mitogen CI test on centos8
(get error  /usr/bin/python: No such file or directory)

docs/ansible.md

@@ -183,3 +183,7 @@ bastion ansible_host=x.x.x.x
 
 For more information about Ansible and bastion hosts, read
 [Running Ansible Through an SSH Bastion Host](https://blog.scottlowe.org/2015/12/24/running-ansible-through-ssh-bastion-host/)
+
+## Mitogen
+
+You can use [mitogen](mitogen.md) to speed up kubespray.

docs/mitogen.md

@@ -0,0 +1,13 @@
+# Mitogen
+
+[Mitogen for Ansible](https://mitogen.networkgenomics.com/ansible_detailed.html) allow a 1.25x - 7x speedup and a CPU usage reduction of at least 2x, depending on network conditions, modules executed, and time already spent by targets on useful work. Mitogen cannot improve a module once it is executing, it can only ensure the module executes as quickly as possible.
+
+## Install
+
+```ShellSession
+ansible-playbook mitogen.yml
+```
+
+## Limitation
+
+If you are experiencing problems, please see the [documentation](https://mitogen.networkgenomics.com/ansible_detailed.html#noteworthy-differences).