Install Guide: Fix Typos In Neutron Compute Node

Similarly to the previous commit, this commit fixes a series of
typos in the compute node section.

This is the third commit in the series

backport: havana

Change-Id: I60916f86788dbc6e2837a4e6245be7aaf83099cd
(cherry picked from commit 55ceae04b0c4e1ff09ed2327559958fa55b1306c)