Add getTetheredDhcpRanges() interface and call it before calling mNwService.startTethering to update dhcp ranges. This will allow p2p apps to run well concurently with other tethering apps. Manual import of AOSP change 81546 by jianzheng.zhou@freescale.com Change-Id: Iebc62f95bdcedde80e2c1d3e9580d3f625c3b50b