Well, you're in a bit of a pickle. Unfortunately for you, Hawaii has no obligation nor stake in finding community service hours for you to fulfill your Cali probation requirements. You now have a warrant for your arrest in CA, and it isn't going to go away by itself. Now, I seriously doubt that CA will extradite you from Hawaii. But, if you ever return to CA and have any police contact, you can expect to be using your phone call to raise bail to get out of jail. Beyond that, since you failed your probation, you can expect that the sentence for your DUI that was suspended will be reinstated.
So, the easy answer is simply don't go back to Cali. But, it really isn't that simple. That warrant is going to show up on every routine background check you have...employment applications, college applications, rental applications, mortgage applications...
My advice would be to retain a lawyer who works in the court where your DUI was adjudicated. An attorney may be able to appear on your behalf and request a further extension for you to complete your community service. Failing that, the attorney will be best able to advise you of your options and negotiate with the court regarding sentencing.

