Update to JGit 4.0.0.201505191015-rc1.19-g1773002

JGit 4 replaced release() with close() throughout the APIs,
which is a breaking change. Most of Gerrit was already using
try-with-resources but a few overrides were impacted.

Change-Id: Ic84e9a6ae87af674a886c2e25734c2d24d06f873

gerrit-server/src/main/java/com/google/gerrit/server/git/MergeUtil.java

@@ -677,7 +677,7 @@ public class MergeUtil {
       }
 
       @Override
-      public void release() {
+      public void close() {
       }
     });
     return (ThreeWayMerger) m;

gerrit-server/src/main/java/com/google/gerrit/server/patch/PatchListLoader.java

@@ -338,7 +338,7 @@ public class PatchListLoader extends CacheLoader<PatchListKey, PatchList> {
         }
 
         @Override
-        public void release() {
+        public void close() {
         }
       });