Add min_sdk_version to DnsResolver tests

Without proper min_sdk_version, the tests might
not be compatible with Q devices.

Test: forrest, atest
Bug: 187907243
Original-Change: https://android-review.googlesource.com/1711570
Merged-In: I9444daad43f036603c5a1cb1460053661f2c79f4
Change-Id: I9444daad43f036603c5a1cb1460053661f2c79f4