Add test to verify multiple messages being received

The original test change in aosp/2243494 did not cover all the
change. The main change was to go through all the messages
instead of stopping reading one time for each IP family.

Add a new test to verify design will go through all the
messages.

Bug: 260938814
Test: atest NetworkStackTests
Change-Id: I9469a2d7960f1ab3d79fabadfac8a1210490ffc3
1 file changed