* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h: Pull old
  qemudDomainGetMemoryBalloon() code into a new method called
  qemuMonitorGetBalloonInfo()
* src/qemu/qemu_driver.c: Update to call qemuMonitorGetBalloonInfo()
  and remove qemudDomainGetMemoryBalloon().