Refactor wifi p2p's startDhcpServer function

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
diff --git a/core/java/android/net/IConnectivityManager.aidl b/core/java/android/net/IConnectivityManager.aidl
index 51d9b8c..7d5dc41 100644
--- a/core/java/android/net/IConnectivityManager.aidl
+++ b/core/java/android/net/IConnectivityManager.aidl
@@ -91,6 +91,8 @@
 
     String[] getTetheringErroredIfaces();
 
+    String[] getTetheredDhcpRanges();
+
     String[] getTetherableUsbRegexs();
 
     String[] getTetherableWifiRegexs();