persist /etc/libvirt/qemu

Libvirt's virsh define command will save vm xml in the
directory /etc/libvirt/qemu/, if it's not persisted, after
the reboot of the os , the defined vm will disapper.
This behavior is not same with the libvirt running on orther os.

Change-Id: I3e9150afd69773d3f2d213da666028b0bcba0660
Signed-off-by: boh.ricky <boh.ricky@gmail.com>