Fix the centos8 default path error in the quickstart.rst document

The openstack Ussuri and Victoria versions no longer support the
Centos7 and pyrhon2 environment packages. Correct the missing
problems in the latest document

Change-Id: I55fd1bf451d2bdae696ab32d1faffaba72701229

doc/source/user/quickstart.rst

@@ -108,7 +108,7 @@ If installing Kolla Ansible in a virtual environment, skip this section.
 
    .. code-block:: console
 
-      sudo pip install -U pip
+      sudo pip3 install -U pip
 
 #. Install `Ansible <http://www.ansible.com>`__. Kolla Ansible requires at least
    Ansible ``2.9`` and supports up to ``2.9``.
@@ -172,7 +172,7 @@ Install Kolla-ansible for deployment or evaluation
 
    .. code-block:: console
 
-      cp -r /usr/share/kolla-ansible/etc_examples/kolla/* /etc/kolla
+      cp -r /usr/local/share/kolla-ansible/etc_examples/kolla/* /etc/kolla
 
    If not using a virtual environment on Ubuntu, run:
 
@@ -193,7 +193,7 @@ Install Kolla-ansible for deployment or evaluation
 
    .. code-block:: console
 
-      cp /usr/share/kolla-ansible/ansible/inventory/* .
+      cp /usr/local/share/kolla-ansible/ansible/inventory/* .
 
    If not using a virtual environment on Ubuntu, run:
 
@@ -536,7 +536,7 @@ Using OpenStack
 
    .. code-block:: console
 
-      pip install python-openstackclient
+      pip install python3-openstackclient
 
 #. OpenStack requires an openrc file where credentials for admin user
    are set. To generate this file: