Add test for NetworkStackUtils.addArpEntry

The test verifies that a DHCP offer can be sent to a fake IP address
when addArpEntry is used to specify a fake MAC address for that host.
It then verifies that the packet was addressed to the fake MAC address.

Test: atest NetworkStackIntegrationTests
Bug: 168868607
Change-Id: Ic6df3724958820b328ca3024aa5a7a7248a7d6d8
1 file changed