Description of problem:
-----------------------
'Additional Hosts' tab at the deployment wizard does 2 checks:
1. FQDN is reachable
2. FQDN is available in known_hosts file

Only when the above 2 conditions are met, it proceeds to the next tab.
But when one valid/legitimate FQDN is provided, along with the illegal FQDN ( either non-reachable or not-in-known_hosts-file, then proceeding to the next tab is no longer dis-allowed


Version-Release number of selected component (if applicable):
-------------------------------------------------------------
cockpit-ovirt-dashboard-0.13.6

How reproducible:
-----------------
Always

Steps to Reproduce:
-------------------
1. Start with the deployment and reach the second tab 'Additional Hosts'
2. Provide one valid FQDN ( FQDN is reachable and exists in known_hosts file )
3. Provide a illegal FQDN ( FQDN not reachable )
4. Click on 'Next'

Actual results:
---------------
The flow proceeds to the next tab

Expected results:
-----------------
The flow should not proceed to next tab, unless the values in additional hosts are legal