libvirt_vm: introduce two method to VM named is_lxc() and is_qemu().

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
libvirt_vm: Make destroy() support lxc.

If the vm is lxc container, we destroy it with virsh command
rather than send a shutdown into it.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
libvirt_vm: Override wait_for_login() method in libvirt_vm.

Override the wait_for_login method of virt_vm to support other
guest in libvirt.

If connect_uri is lxc related, we call wait_for_serial_login()
directly, without attampting login it via network.

Other connect_uri, call virt_vm.wait_for_login().

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
libvirt_vm: make normalize_connect_uri return exact uri rather than None when input is default.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
libvirt_vm: Fix for vm.connect_uri when it is default.

Default is not always qemu.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
libvirt_vm: send ^] to serial_console when vm is lxc to close console.

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