UI fails silently on cluster setup page when configuring hostname incorrectly

The issue is very similar to MB-46419, except that we should also report POST /nodeInit errors if the hostname is incorrect. 
For example, if you set the hostname incorrectly as "localhost" (instead of fully qualified domain name "localhost.localdomain"), UI would fail silently
and the actual response from /nodeInit is like this:

{"errors":{"hostname":"Requested hostname \"localhost\" is not allowed: Short names are not allowed. Please use a Fully Qualified Domain Name."}}

Setting this to Minor (as we have mention on UI to provide FQ domain-name), and hence setting the fix-version to CC.next. Please change the fix-version to CC if you think otherwise.