Data stall detection using DNS event

If dns resolver on a network get consecutively timeout then it
is a strong signal that the network is no longer usable.
Reevaluate the network once it's data stall suspected

Test: 1. runtest frameworks-net
      2. SettingsBackupTest passes
      2. Run on wifi w/o internet capability
Bug: 112653893, 113916551

Change-Id: I74287b174d933f97a91fa1529b1809856ac3b38d