qemu: Avoid false failure when resuming post-copy migration

qemu: Avoid false failure when resuming post-copy migration

Depending on timing between QEMU and libvirt an attempt to resume failed
post-copy migration could immediately report a failure in post-copy
phase again even though the migration actually resumed and is
progressing just fine.

This is caused by QEMU reporting the original migration state (i.e.,
postcopy-paused) until migration is successfully resumed and QEMU
switches to postcopy-active. QEMU 9.1 introduced a new
postcopy-recover-setup migration state which is entered immediately
after requesting migration to be resumed and we can reliably wait for
the migration to either continue or fail without being confused by the
old state.

https://issues.redhat.com/browse/RHEL-22166

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>