Add NetworkStack tests to postsubmit

The NetworkStack tests were unit tests in FrameworksNetTests, but were
moved out so were no longer run in presubmit.
After a while the tests should be moved to presubmit.

Test: atest NetworkStackTests
Change-Id: I06ddcafd6de6d9029ac710f0fc3c4f2d1d705c01
1 file changed