fix netboot installshim stuck in DHCP netboot use busybox ifconfig and this output is different with usb install shim. Use ip to get network information. 'ip -f link addr' to show all interfaces and filter ether type. 'ip -f inet addr' to show all interfaces which have IP address. BUG=chrome-os-partner:24442 TEST=manually test for netboot CQ-DEPEND=CL:180153 Change-Id: I26032416e3022d8034e4b165ac94a3be49e2602a Reviewed-on: https://chromium-review.googlesource.com/179396 Reviewed-by: Heng-ruey Hsu <[email protected]> Commit-Queue: Heng-ruey Hsu <[email protected]> Tested-by: Heng-ruey Hsu <[email protected]>