Clarify Ansible installation for distros in docs.

For CentOS, install from distro packaging by default.  Explain
how to install on DEB based systems from packaging when they
update to a newer version of Ansible.  Finally, clean up the
ordering of the dependencies for a pip based install.

TrivialFix

Change-Id: I9564a03c2e75fd30b5ec9c7d64f5defb709d7fde

doc/quickstart.rst

@@ -181,36 +181,43 @@ Kolla deploys OpenStack using
 `Ansible <http://www.ansible.com>`__. Install Ansible from distribution
 packaging if the distro packaging has recommended version available.
 
-Currently all implemented distro versions of Ansible are too old to use distro
-packaging.  Once distro packaging is updated install from packaging using:
+Some implemented distro versions of Ansible are too old to use distro
+packaging.  Currently, CentOS and RHEL package Ansible 1.9.4 which is 
+suitable for use with Kolla. 
+
+On CentOS or RHEL systems, this can be done using:
 
 ::
 
     yum -y install ansible
 
-On DEB based systems this can be done using:
+Many DEB based systems do not meet Kolla's Ansible version requirements.
+It is recommended to use pip to install Ansible 1.9.4.
+
+Some ansible dependencies, like pycrypto, may need gcc installed on the build
+system. Install it using system packaging tools if it's not installed already:
 
 ::
 
-    apt-get install ansible
+    # Centos 7
+    yum -y install gcc
 
-If the distro packaged version of Ansible is too old, install Ansible using
-pip:
+    # Ubuntu
+    sudo apt-get install gcc
+
+Finally Ansible 1.9.4 may be installed using:
 
 ::
 
-    pip install -U ansible
+    pip install -U ansible==1.9.4
 
-Some ansible dependencies, like pycrypto, may need gcc installed on the build
-system. Install it using system packaging tools if it's not installed already:
+If DEB based systems include a version of Ansible that meets Kolla's
+version requirements it can be installed by:
 
 ::
 
-    # Centos 7
-    yum -y install gcc
+    apt-get install ansible
 
-    # Ubuntu
-    sudo apt-get install gcc
 
 Deploy a registry (required for multinode)
 ------------------------------------------