virt-libvirt_vm: add a method get_key2value_from_key2path in libvirt_vm.

def get_key2value_from_key2path(key2path_dict={}):
    """
    Get the values stored in files whose path is in key2path_dict.

    @param key2path_dict: dict stored key and the path.
    @return: dict stored key and the value.
    """

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
virt-virsh: add a method for nodedev-dumpxml and nodedev-list.

def nodedev_list(cap=None, tree=False, **dargs):
    """
    List the node devices.

    @return: CmdResult object.
    """
def nodedev_dumpxml(name, **dargs):
    """
    Do dumpxml for node device.

    @param name: the name of device.
    @return: string for xml of device.
    """

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
virt-libvirt: add configuration and test module for virsh nodede-dump.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>