(1) Move the following APIs from base/util.h to net/address.cc/h
GetIp6SubnetAddress
GetIp4SubnetAddress

(2) Also change the signature of API IsIp4SubnetMember and IsIp6SubnetMember to use aliases Ip4Address/Ip6Address instead of boost names.

(3) Update the callers to use the new moved API from address.cc

All the existing agent Unit test-cases have passed

Change-Id: I15844c52eefe5d88050285d1fcfc2e80e294bd63
Closes-Bug: #1381334
Merge "(1) Move the following APIs from base/util.h to net/address.cc/h GetIp6SubnetAddress GetIp4SubnetAddress"