autotest/virt-test — pull request #1926 by PandaWei (2014-12-18 10:17:41+00:00)
Title: Add slots of channel and Add get_dev_pts_max_id()  for hotplug serial test 

1.libvirt_xml.devices: Add slots for channel.
The latest slots includes 'alias' and 'address'.

2. virttest.utils_misc: add function to get the maxi ID for pty chardev
when hot-pluging in pseudoterminal interfaces to VM for pty device,
we must specify the device source path (/dev/pts/) for it.
The function get_dev_pts_max_id() can used to get the maxi and
occupied device number.
and then, user can specify the available source path based on it.