Skip connectivity unit tests before S

The tests are packaged together with other tests in a common coverage
suite, so need to be individually annotated so that they are skipped
before S.

They do not need to pass on platforms older than S, because such
platforms will not updated with the code that is tested.

Bug: 187935317
Test: atest ConnectivityCoverageTests on R
Change-Id: I10da45ae023e7f1e8cd11ec857b84346892a3fa8

tests/unit/java/android/net/util/DnsUtilsTest.java

@@ -25,7 +25,9 @@ import static org.junit.Assert.assertEquals;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.net.InetAddresses;
+import android.os.Build;
 
+import androidx.test.filters.SdkSuppress;
 import androidx.test.filters.SmallTest;
 import androidx.test.runner.AndroidJUnit4;
 
@@ -39,6 +41,7 @@ import java.util.List;
 
 @RunWith(AndroidJUnit4.class)
 @SmallTest
+@SdkSuppress(minSdkVersion = Build.VERSION_CODES.S, codeName = "S")
 public class DnsUtilsTest {
     private InetAddress stringToAddress(@NonNull String addr) {
         return InetAddresses.parseNumericAddress(addr);

tests/unit/java/android/net/util/KeepaliveUtilsTest.kt

@@ -25,6 +25,8 @@ import android.net.NetworkCapabilities.TRANSPORT_CELLULAR
 import android.net.NetworkCapabilities.TRANSPORT_ETHERNET
 import android.net.NetworkCapabilities.TRANSPORT_VPN
 import android.net.NetworkCapabilities.TRANSPORT_WIFI
+import android.os.Build
+import androidx.test.filters.SdkSuppress
 import androidx.test.filters.SmallTest
 import com.android.internal.R
 import org.junit.After
@@ -47,6 +49,7 @@ import org.mockito.Mockito.mock
  */
 @RunWith(JUnit4::class)
 @SmallTest
+@SdkSuppress(minSdkVersion = Build.VERSION_CODES.S, codeName = "S")
 class KeepaliveUtilsTest {
 
     // Prepare mocked context with given resource strings.

tests/unit/java/android/net/util/MultinetworkPolicyTrackerTest.kt

@@ -25,11 +25,13 @@ import android.net.ConnectivityResources
 import android.net.ConnectivitySettingsManager.NETWORK_AVOID_BAD_WIFI
 import android.net.ConnectivitySettingsManager.NETWORK_METERED_MULTIPATH_PREFERENCE
 import android.net.util.MultinetworkPolicyTracker.ActiveDataSubscriptionIdListener
+import android.os.Build
 import android.provider.Settings
 import android.telephony.SubscriptionInfo
 import android.telephony.SubscriptionManager
 import android.telephony.TelephonyManager
 import android.test.mock.MockContentResolver
+import androidx.test.filters.SdkSuppress
 import androidx.test.filters.SmallTest
 import androidx.test.runner.AndroidJUnit4
 import com.android.connectivity.resources.R
@@ -59,6 +61,7 @@ import org.mockito.Mockito.verify
  */
 @RunWith(AndroidJUnit4::class)
 @SmallTest
+@SdkSuppress(minSdkVersion = Build.VERSION_CODES.S, codeName = "S")
 class MultinetworkPolicyTrackerTest {
     private val resources = mock(Resources::class.java).also {
         doReturn(R.integer.config_networkAvoidBadWifi).`when`(it).getIdentifier(