Fixes get-started guide
Fixes get-started guide

Tacker provide guidelines to install it manually or
using devstack, so its good to make the get-start guide
to be neutral to the installation process.

Change-Id: I29152831925ece616419aec9facd39770bdf19ed

zeinsteinz/tacker,trozet/tacker,openstack/tacker,openstack/tacker,priya-pp/Tacker,stackforge/tacker,zeinsteinz/tacker,stackforge/tacker,priya-pp/Tacker,trozet/tacker,openstack/tacker