Block SDK 28 app from using proc/net/xt_qtaguid

The file under /proc/net/xt_qtaguid is going away in future release.
Apps should use the provided public api instead of directly reading the
proc file. This change will block apps that based on SDK 28 or above to
directly read that file and we will delete that file after apps move
away from it.

Test: Flashed with master branch on marlin, verified phone boot, can
      browse web, watch youtube video, make phone call and use google
      map for navigation with wifi on and off.
      run cts -m CtsNetTestCases -t android.net.cts.TrafficStatsTest
      run cts -m CtsAppSecurityHostTestCases -t \
      		android.appsecurity.cts.AppSecurityTests

Change-Id: I4c4d6c9ab28b426acef23db53f171de8f20be1dc