Bump min Ansible version to 2.2.0

Different Y stream version in Ansible is not compatible. Since ansible
2.2.0 is released for a while. It is time for kolla-ansible to bump the
min Ansible version. Then we can remove the annoying WARNING message
in deploying logs and use the new features.

Change-Id: I99f3c5678f6d2d1f93d61c660fbd166184ff6422

ansible/roles/prechecks/vars/main.yml

 ---
 docker_version_min: '1.10.0'
 docker_py_version_min: '1.8.1'
-ansible_version_min: '2.0.0'
+ansible_version_min: '2.2.0'

doc/quickstart.rst

@@ -87,8 +87,7 @@ Docker Python           1.6.0        none         On target nodes
 Python Jinja2           2.8.0        none         On deployment host
 =====================   ===========  ===========  =========================
 
-Dependencies for the stable/ocata branch and later (including master branch)
-are:
+Dependencies for the stable/ocata branch are:
 
 =====================   ===========  ===========  =========================
 Component               Min Version  Max Version  Comment
@@ -99,6 +98,17 @@ Docker Python           1.8.1        none         On target nodes
 Python Jinja2           2.8.0        none         On deployment host
 =====================   ===========  ===========  =========================
 
+Dependencies since pike (including master branch) are:
+
+=====================   ===========  ===========  =========================
+Component               Min Version  Max Version  Comment
+=====================   ===========  ===========  =========================
+Ansible                 2.2.0        none         On deployment host
+Docker                  1.10.0       none         On target nodes
+Docker Python           1.8.1        none         On target nodes
+Python Jinja2           2.8.0        none         On deployment host
+=====================   ===========  ===========  =========================
+
 Make sure the ``pip`` package manager is installed and upgraded to the latest
 before proceeding: