Previously drbbdup failed to restore the state for its own register spills. We add a restore state event here, for the case where we have an ilist.
Tested on the drcacheoff.burst_threads test. With a higher loop count for the other threads, detach hits each instruction of the drbbdup dispatch code with repeated runs and in manual testing I verified the details of each. It is difficult to construct a deterministic test of asynch translation at these constrained points.
Issue: #5686