virt: fix prompt in VirshSession to support prompt 'virsh >'

When connect --readonly in a virsh session, the prompt changes to 'virsh >'.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
virt: Add connect function into virsh module.

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

Well, there are so many transport type in uri.
This module is designed as 3-host model(client,
server and admin) referring to
http://wiki.libvirt.org/page/TLSSetup.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
virt: add method 'get_uri_with_transport' into libvirt_vm.

def get_uri_with_transport(origin_uri="qemu:///system", transport="",
                            dest_ip=""):
    """
    Return a URI to connect driver on dest with a specificed transport.

    @param origin_uri: The URI on dest used to connect itself directly.
    @param transport: The transport type connect to dest.
    @param dest_ip: The ip of destination.
    """

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
virt: fixup virsh connect test module and configuration.

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