qemu: Refactor qemuDomainGetJobInfoMigrationStats
qemu: Refactor qemuDomainGetJobInfoMigrationStats

The code was a bit too complicated, especially after removing the check
for QEMU_CAPS_MIGRATION_EVENT.

Signed-off-by: Jiri Denemark <62bdf77dc47919a4d59a91822129d14633cfca81@redhat.com>
Reviewed-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>

crobinso/libvirt,olafhering/libvirt,jfehlig/libvirt,zippy2/libvirt,libvirt/libvirt,zippy2/libvirt,crobinso/libvirt,libvirt/libvirt,jfehlig/libvirt,crobinso/libvirt,olafhering/libvirt,libvirt/libvirt,olafhering/libvirt,jfehlig/libvirt,zippy2/libvirt,zippy2/libvirt,jfehlig/libvirt,olafhering/libvirt,libvirt/libvirt,crobinso/libvirt