Add a method named sub_else_add in RemoteFile class.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
Add utils_conn module in virttest.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
Add test for virsh connect.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
Fix virsh.py: Remove the function not defined calling.

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