Remove explicit initialization of default values

Default values are false for boolean, 0 for int and char, and null
for object references.

Explicitly initializing a variable to the default value causes it
to be initialized twice.

Enable the Checkstyle warning, and fix occurences of it.

Change-Id: I1971e438fc506c18458b1402fcb01e43fa61ff8c

gerrit-server/src/main/java/com/google/gerrit/server/project/RefControl.java

@@ -473,8 +473,8 @@ public class RefControl {
   }
 
   private static class AllowedRange {
-    private int allowMin = 0;
-    private int allowMax = 0;
+    private int allowMin;
+    private int allowMax;
     private int blockMin = Integer.MIN_VALUE;
     private int blockMax = Integer.MAX_VALUE;