Is this specifically for an AJAX call?

This could cause problems too because sometimes there is a lag between when a DNS is updated and the information is propgated.

Yes there are all sorts of the delays. It is for the case when you are adding a host or service manually. It is assumed that you do not know if the DNS entry was already added some time ago or not. If it was added recently you probably would not try to resolve or ignore if it gives you warnings because you know that there is a DNS propagation latency.

This is a very simple resolver. You really should pass in the FQDN of the host you want to resolve. It will add on the IPA default domain if you don't but it doesn't do any other fancy footwork.

simple dns resolver, with tests
freeipa-533-lookup.patch

master: 89d2280

For QE, this is just used so the UI can see if a hostname is in DNS or not, it doesn't do anything really clever on output:

ipa dns-resolve www.freeipa.org
-----------------------
Found 'www.freeipa.org.'

ipa dns-resolve unknown.freeipa.org
ipa: ERROR: Host 'unknown.freeipa.org.' not found