Update import class from TrafficStatsConstants to NetworkStackConstants

Some constants in TrafficStatsConstants are moved to
NetworkStackConstants so update the import class to use the constants.

Bug: 182349970
Test: FrameworksNetTests
      NetworkStackTests
      TetheringTests
Change-Id: Iaab5d721bb3b9536f560ad12436530150e03c370
Merged-In: Iaab5d721bb3b9536f560ad12436530150e03c370
4 files changed