Correct the order of import and remove unused definition

Test: atest
Change-Id: I60c409db5436a5ba9fffdee9df24158f15751658
diff --git a/tests/common/java/android/net/NattKeepalivePacketDataTest.kt b/tests/common/java/android/net/NattKeepalivePacketDataTest.kt
index ad7a526..a7d1115 100644
--- a/tests/common/java/android/net/NattKeepalivePacketDataTest.kt
+++ b/tests/common/java/android/net/NattKeepalivePacketDataTest.kt
@@ -22,9 +22,9 @@
 import android.os.Build
 import androidx.test.filters.SmallTest
 import androidx.test.runner.AndroidJUnit4
-import com.android.testutils.assertEqualBothWays
 import com.android.testutils.DevSdkIgnoreRule
 import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo
+import com.android.testutils.assertEqualBothWays
 import com.android.testutils.assertParcelingIsLossless
 import com.android.testutils.parcelingRoundTrip
 import java.net.InetAddress
@@ -41,10 +41,6 @@
     @Rule @JvmField
     val ignoreRule: DevSdkIgnoreRule = DevSdkIgnoreRule()
 
-    /* Refer to the definition in {@code NattKeepalivePacketData} */
-    private val IPV4_HEADER_LENGTH = 20
-    private val UDP_HEADER_LENGTH = 8
-
     private val TEST_PORT = 4243
     private val TEST_PORT2 = 4244
     private val TEST_SRC_ADDRV4 = "198.168.0.2".address()
@@ -108,4 +104,4 @@
     fun testHashCode() {
         assertEquals(nattKeepalivePacket().hashCode(), nattKeepalivePacket().hashCode())
     }
-}
\ No newline at end of file
+}