8.0.0: Crash when attempting to commit snapshot
Description of problem:
When trying to commit a snapshot to the backing store, qemu exits with the error:

`qemu: qemu_mutex_unlock_impl: Operation not permitted`
Steps to reproduce:
1. Run qemu command above
2. Open the monitor virtual console (Ctrl-Alt-2)
3. Execute command: `commit os`
Additional information:
Attached are the [backtrace](/uploads/ba8f519e6b00eb054ba416054c782122/8.0.0-1-bt) and the [configure output](/uploads/17124b45e12b252bd01cf41e7a3d2ea4/8.0.0-1-conf.gz). This is a regression from 7.2.1