Care to elaborate on that? I don't see any error in my setup (it works fine).
I have one dedicated mysql server that hosts the main ISPConfig database and the local slave database, so the ispconfig install on this machine (this is a slave machine) has the conf["dbmaster_host"] and $conf["db_host"] being 'localhost' since both databases are on the local machine.
Note that I do NOT have mysql on my ISPConfig master server!
The dbNames of both are evidently different, and I think you should put your check on those and not on the actual servername.
One can easily fix this by changing one of both to a local alias af course, but that's not the cleanest solution.