services: fix lint warnings on binlog (#3927)

diff --git a/services/src/main/java/io/grpc/services/BinaryLog.java b/services/src/main/java/io/grpc/services/BinaryLog.java
index 6e1f74b..522051b 100644
--- a/services/src/main/java/io/grpc/services/BinaryLog.java
+++ b/services/src/main/java/io/grpc/services/BinaryLog.java
@@ -19,6 +19,7 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Objects;
 import com.google.common.base.Preconditions;
+import com.google.common.base.Splitter;
 import com.google.common.primitives.Bytes;
 import com.google.protobuf.ByteString;
 import io.grpc.InternalMetadata;
@@ -145,8 +146,7 @@
       Map<String, BinaryLog> perServiceLogs = new HashMap<String, BinaryLog>();
       Map<String, BinaryLog> perMethodLogs = new HashMap<String, BinaryLog>();
 
-      String[] configurations = configurationString.split(",");
-      for (String configuration : configurations) {
+      for (String configuration : Splitter.on(',').split(configurationString)) {
         Matcher configMatcher = configRe.matcher(configuration);
         if (!configMatcher.matches()) {
           throw new IllegalArgumentException("Bad input: " + configuration);
@@ -273,7 +273,8 @@
   // TODO(zpencer): verify int64 representation with other gRPC languages
   static Uint128 callIdToProto(byte[] bytes) {
     Preconditions.checkArgument(
-        bytes.length == 16, "can only convert from 16 byte input, actual length =" + bytes.length);
+        bytes.length == 16,
+        String.format("can only convert from 16 byte input, actual length = %d", bytes.length));
     ByteBuffer bb = ByteBuffer.wrap(bytes);
     long high = bb.getLong();
     long low = bb.getLong();
diff --git a/services/src/test/java/io/grpc/services/BinaryLogTest.java b/services/src/test/java/io/grpc/services/BinaryLogTest.java
index fa59977..de95d15 100644
--- a/services/src/test/java/io/grpc/services/BinaryLogTest.java
+++ b/services/src/test/java/io/grpc/services/BinaryLogTest.java
@@ -54,9 +54,9 @@
   private static final BinaryLog BOTH_FULL =
       new Builder().header(Integer.MAX_VALUE).msg(Integer.MAX_VALUE).build();
 
-  private static final String dataA = "aaaaaaaaa";
-  private static final String dataB = "bbbbbbbbb";
-  private static final String dataC = "ccccccccc";
+  private static final String DATA_A = "aaaaaaaaa";
+  private static final String DATA_B = "bbbbbbbbb";
+  private static final String DATA_C = "ccccccccc";
   private static final Metadata.Key<String> KEY_A =
       Metadata.Key.of("a", Metadata.ASCII_STRING_MARSHALLER);
   private static final Metadata.Key<String> KEY_B =
@@ -67,19 +67,19 @@
         MetadataEntry
             .newBuilder()
             .setKey(ByteString.copyFrom(KEY_A.name(), US_ASCII))
-            .setValue(ByteString.copyFrom(dataA.getBytes(US_ASCII)))
+            .setValue(ByteString.copyFrom(DATA_A.getBytes(US_ASCII)))
             .build();
   private static final MetadataEntry ENTRY_B =
         MetadataEntry
             .newBuilder()
             .setKey(ByteString.copyFrom(KEY_B.name(), US_ASCII))
-            .setValue(ByteString.copyFrom(dataB.getBytes(US_ASCII)))
+            .setValue(ByteString.copyFrom(DATA_B.getBytes(US_ASCII)))
             .build();
   private static final MetadataEntry ENTRY_C =
         MetadataEntry
             .newBuilder()
             .setKey(ByteString.copyFrom(KEY_C.name(), US_ASCII))
-            .setValue(ByteString.copyFrom(dataC.getBytes(US_ASCII)))
+            .setValue(ByteString.copyFrom(DATA_C.getBytes(US_ASCII)))
             .build();
   private static final boolean IS_COMPRESSED = true;
   private static final boolean IS_UNCOMPRESSED = false;
@@ -88,9 +88,9 @@
 
   @Before
   public void setUp() throws Exception {
-    metadata.put(KEY_A, dataA);
-    metadata.put(KEY_B, dataB);
-    metadata.put(KEY_C, dataC);
+    metadata.put(KEY_A, DATA_A);
+    metadata.put(KEY_B, DATA_B);
+    metadata.put(KEY_C, DATA_C);
   }
 
   @Test
@@ -373,15 +373,11 @@
   public void metadataToProto_truncated() throws Exception {
     // 0 byte limit not enough for any metadata
     assertEquals(
-        io.grpc.binarylog.Metadata
-            .newBuilder()
-            .build(),
+        io.grpc.binarylog.Metadata.getDefaultInstance(),
         BinaryLog.metadataToProto(metadata, 0));
     // not enough bytes for first key value
     assertEquals(
-        io.grpc.binarylog.Metadata
-            .newBuilder()
-            .build(),
+        io.grpc.binarylog.Metadata.getDefaultInstance(),
         BinaryLog.metadataToProto(metadata, 9));
     // enough for first key value
     assertEquals(