d8e4e552ec
When we're shutting down, we send a number of start/stop commands to the known targets. We have to wait for them to complete. During a panic, the interrupts are off, and using pause to wait for them to fire and complete won't work: we have to poll after pause returns so the completion routines of the CCBs run so we decrement work outstanding counts. Sponsored by: Netflix Differential Review: https://reviews.freebsd.org/D16663