Use correct SLF4J log format strings

These use braces for placeholders instead of %s like normal Java
logging.

Change-Id: I48b135879e391159c3ec5d7bbd4abc2862a75c05

gitiles-dev/src/main/java/com/google/gitiles/dev/DevServer.java

diff --git a/gitiles-dev/src/main/java/com/google/gitiles/dev/DevServer.java b/gitiles-dev/src/main/java/com/google/gitiles/dev/DevServer.java
index a52b4e3..2a2ef1e 100644
--- a/gitiles-dev/src/main/java/com/google/gitiles/dev/DevServer.java
+++ b/gitiles-dev/src/main/java/com/google/gitiles/dev/DevServer.java
@@ -140,7 +140,7 @@
     } else {
       // TODO(dborowitz): This is not getting outputted, we're probably missing
       // some logging config.
-      log.info("Config file %s not found, using defaults", cfgFile.getPath());
+      log.info("Config file {} not found, using defaults", cfgFile.getPath());
     }
     this.cfg = cfg;
 

gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java

diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java
index 2594d08..387e342 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java
@@ -171,7 +171,7 @@
           showGitlink(req, res, rw, tw, root, hasSingleTree);
           break;
         default:
-          log.error("Bad file type: %s", type);
+          log.error("Bad file type: {}", type);
           res.setStatus(SC_NOT_FOUND);
           break;
       }

gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java

diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java
index 345f7d2..c2eacdf 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java
@@ -95,7 +95,7 @@
                   "data", new TagSoyData(linkifier, req).toSoyData((RevTag) obj)));
               break;
             default:
-              log.warn("Bad object type for %s: %s", ObjectId.toString(obj.getId()), obj.getType());
+              log.warn("Bad object type for {}: {}", ObjectId.toString(obj.getId()), obj.getType());
               res.setStatus(SC_NOT_FOUND);
               return;
           }