To date, JSON disk snapshots worked by accident, as they were always
using hmp fallback due to a typo in commit e702b5b not picking up
on the (intentional) difference in command names between the two
monitor protocols.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONDiskSnapshot):
Spell QMP command correctly.
Reported by Luiz Capitulino.