virtttest : add restart nic and get nic attributes of windows guest

This patch add function support restart windows guest network,
except winxp. add function to get windows nic attributes(like nic index,
netconnectionid, macaddress ans so on, you can get all support
attributes by 'wmic nic get ').
qemu : add mac_change support windows

This patch make mac_change case support windows guest, except WinXP
qemu : Modify configure for jumbo test support windows guest

This patch make case jumbo test support windows except winxp
Using iperf test guest nic multicast

This patch using iperf test guest nic multicast, support both
linux and windos guest.