Use the net-utils-device-common version of HexDump

KeepaliveTracker is included in ConnectivityService mainline
module and it will not be able to access internal util class
com.android.internal.util.HexDump. Use the HexDump defined in
net-utils-device-common to remove dependency on internal util
class.

Bug: 177046265
Test: FrameworksNetTests
Change-Id: I1f5a6a749106b98e2baf22d6a290dcf8b51a6c36
diff --git a/services/core/java/com/android/server/connectivity/KeepaliveTracker.java b/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
index 34d9ccc..7b20ded 100644
--- a/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
+++ b/services/core/java/com/android/server/connectivity/KeepaliveTracker.java
@@ -57,8 +57,8 @@
 import android.util.Pair;
 
 import com.android.internal.R;
-import com.android.internal.util.HexDump;
 import com.android.internal.util.IndentingPrintWriter;
+import com.android.net.module.util.HexDump;
 import com.android.net.module.util.IpUtils;
 
 import java.io.FileDescriptor;