Description of problem:
Generate inventory with "--gen-inventory" against existed cluster. After printing "Installation Summary", it will ask user to make an unrelated choice about if re-install or not.

Version-Release number of selected component (if applicable):
atomic-openshift-utils-3.4.32-1.git.0.076b279.el7.noarch

How reproducible:
always

Steps to Reproduce:
1. Installing a cluster by quick-install first
2. Try to generate inventory host for the cluster above by the existing installer.cfg.yml 
#atomic-openshift-installer install --gen-inventory
3. it will detect the cluster has been installed and ask user to reinstall or not after output "Installation Summary"
<--snip-->
All specified hosts in specified environment are installed.

Do you want to (re)install the environment?

Note: This will potentially erase any custom changes. [y/N]:
<--snip-->

3.

Actual results:
1)If choose 'n', it will exit with following hint mesaage:

If you want to force reinstall of your environment, run:
`atomic-openshift-installer install --force`

If you want to add new nodes to this environment, run:
`atomic-openshift-installer scaleup`

2)If choose 'y', it will exit with following hint message about generated files:

Wrote atomic-openshift-installer config: /root/.config/openshift/installer.cfg.yml
Wrote Ansible inventory: /root/.config/openshift/hosts

Expected results:
It should not include redundant re-install process when run quick install with "--gen-inventory", instead, installer should generate the inventory hosts that the users expect.