destroyContainerFS must wait for all async operations to finish before
returning. In an attempt to do this, we call fs.AsyncBarrier() at the end of
the function. However, there are many defer'd DecRefs which end up running
AFTER the AsyncBarrier() call.
This CL fixes this by calling fs.AsyncBarrier() in the first defer statement,
thus ensuring that it runs at the end of the function, after all other defers.
PiperOrigin-RevId: 220523545
Change-Id: I5e96ee9ea6d86eeab788ff964484c50ef7f64a2f