Call ConnectivitySettingsUtils to set/get private DNS related settings

ConnectivitySettingsManager and CtsNetUtils are doing the same
thing to set/get private DNS related settings.
To prevent making the duplication code in two places, move the
body to frameworks/libs/net and call it.

Bug: 185311744
Test: atest CtsNetTestCases CtsNetTestCasesLatestSdk
Original-Change: https://android-review.googlesource.com/1719017
Merged-In: I3272c825b86ec30c3d0bf4097088c653e668461b
Change-Id: I3272c825b86ec30c3d0bf4097088c653e668461b
3 files changed