follow up: Fix the centos8 default path error in the quickstart.rst document

fix the rest of  mistakes, and remove duplicated line.

Change-Id: Id50dfd9cfa794526bdb69ee6372a29c0584310d3

doc/source/user/quickstart.rst

@@ -151,7 +151,7 @@ Install Kolla-ansible for deployment or evaluation
 
    .. code-block:: console
 
-      sudo pip install kolla-ansible
+      sudo pip3 install kolla-ansible
 
 #. Create the ``/etc/kolla`` directory.
 
@@ -168,13 +168,7 @@ Install Kolla-ansible for deployment or evaluation
 
       cp -r /path/to/venv/share/kolla-ansible/etc_examples/kolla/* /etc/kolla
 
-   If not using a virtual environment on CentOS or RHEL, run:
-
-   .. code-block:: console
-
-      cp -r /usr/local/share/kolla-ansible/etc_examples/kolla/* /etc/kolla
-
-   If not using a virtual environment on Ubuntu, run:
+   If not using a virtual environment, run:
 
    .. code-block:: console
 
@@ -189,13 +183,7 @@ Install Kolla-ansible for deployment or evaluation
 
       cp /path/to/venv/share/kolla-ansible/ansible/inventory/* .
 
-   If not using a virtual environment on CentOS or RHEL, run:
-
-   .. code-block:: console
-
-      cp /usr/local/share/kolla-ansible/ansible/inventory/* .
-
-   If not using a virtual environment on Ubuntu, run:
+   If not using a virtual environment, run:
 
    .. code-block:: console
 
@@ -224,8 +212,8 @@ Install Kolla for development
 
    .. code-block:: console
 
-      sudo pip install ./kolla
-      sudo pip install ./kolla-ansible
+      sudo pip3 install ./kolla
+      sudo pip3 install ./kolla-ansible
 
 #. Create the ``/etc/kolla`` directory.
 
@@ -560,13 +548,7 @@ Using OpenStack
    create example networks, images, and so on.
 
    * For deployment or evaluation,
-     run ``init-runonce`` script on CentOS or RHEL:
-
-     .. code-block:: console
-
-        /usr/share/kolla-ansible/init-runonce
-
-     Run ``init-runonce`` script on Ubuntu:
+     run ``init-runonce`` script:
 
      .. code-block:: console