qemu-img is going to switch the default for QCOW2
to QCOW2v3 (compat=1.1)
Extend the probing for qemu-img command line options to check
if -o compat is supported. If the volume definition specifies
the qcow2 format but no compat level and -o compat is supported,
specify -o compat=0.10 to create a QCOW2v2 image.
https://bugzilla.redhat.com/show_bug.cgi?id=997977
