code-block replaces the soucecode in install docs section
code-block replaces the soucecode in install docs section

https://docs.openstack.org/sahara/wallaby/install/installation-guide.html#common-installation-steps
cannot show the doc's content with soucecodes, instead of using
code-block.

Change-Id: Ie6e2a6c9c9a27cbd976fb3d973f36f02f5b20a96

openstack/sahara,openstack/sahara