steffkes: your patch applies cleanly, but didn't compile – it looks like you modified some files that weren't included in the patch?
based on the hoops it looked like you were having to jump through to track this, i looked at where/how/why were were throwing away the core name if it was the default core, and took a crack at just undo-ing that mess so that every core knows it's real and true name – and only the CoreContainer worries about what the name of the default core is – this only required two tweaks to tests (and one of those was to eliminate special hoops TestJmxIntegration was jumping through to get the right name if the core was the default!)
Once that was done, CoreAdminHandler seemed to return consistent name info in the status for every core, regardless of how many there were, or if a default name was in use. So then since i figured it would be handy, i added the defaultCoreName to the output when you get status for all cores (either a string or null if there is no default core name) and for good measure i also put an "isDefault" boolean in the status for each core.
try this out and see if does everything you need/want to make the UI go vroom ... like i said, all tests pass for me, but i don't want to commit w/o some review from miller – this fix seems so easy i don't understand why the logic was reversed before, so i'm scared i may be missing something