Add notes to provide more clarity for bifrost installation

Included activation block so that new users will not skip activating their virtual environment.
To prevent bridge interface error during installation via playbooks, a note is included
to notify users using virtual environment not to change the ``network_interface``.
The commands in the playbook execution section under advanced installation is placed in
a code block for better readability.
Added more context to  virtual env network interface
DocImpact

Change-Id: I6079591f264fb2822b7afb6afeebd1555da8e226

Author: adesinaadeola

doc/source/install/index.rst

@@ -327,6 +327,13 @@ After installation is done, export the following environment variable to
 configure the bare metal client to use the ``bifrost`` cloud configuration from
 the generated ``clouds.yaml`` (see :ref:`baremetal-cli` for details):
 
+.. note::
+   When using bifrost in a virtual environment, ensure to activate it.
+
+.. code-block:: shell
+
+   source ~/bifrost/env/bin/activate
+
 .. code-block:: shell
 
    export OS_CLOUD=bifrost

doc/source/install/playbooks.rst

@@ -76,6 +76,7 @@ upon.
   your local installation.
 - Change ``network_interface`` to match the interface that will need
   to service DHCP requests.
+
 - Set ``service_password`` which is used for communication between services.
   If unset, a random password is generated during the initial installation and
   stored on the controller in ``~/.config/bifrost/service_password``.
@@ -184,19 +185,25 @@ First, make sure that the virtual environment is active (the example below
 assumes that bifrost venv is installed into the default path
 /opt/stack/bifrost).
 
+.. code-block:: bash
+
     $ . /opt/stack/bifrost/bin/activate
-    (bifrost) $
+    (bifrost)$
 
 Verify if the ansible-playbook executable points to the one installed in
 the virtual environment:
 
-    (bifrost) $ which ansible-playbook
-    /opt/stack/bifrost/bin/ansible-playbook
-    (bifrost) $
+.. code-block:: bash
+
+   (bifrost)$ which ansible-playbook
+   /opt/stack/bifrost/bin/ansible-playbook
+   (bifrost)$
 
 change to the ``playbooks`` subdirectory of the cloned bifrost repository:
 
-    $ cd playbooks
+.. code-block:: bash
+
+   $ cd playbooks
 
 If you have passwordless sudo enabled, run::