In some circumstances, libvirtd would issue two STOPPED events after it
stopped a domain. This was because an EOF event can arrive after a qemu
process is killed but before qemuMonitorClose() is called.

qemuHandleMonitorEOF() should ignore EOF when the domain is not running.

I wasn't able to reproduce this bug directly, only after adding an
artificial sleep() into qemudShutdownVMDaemon().