Making nested class static.

This class is very frequently used and instantiated,
but there is no need to have it non-static. Having is
static is "cheaper",

nexus/nexus-api/src/main/java/org/sonatype/nexus/proxy/item/ReadLockingContentLocator.java

@@ -66,7 +66,7 @@ public InputStream getContent()
 
     // ==
 
-    private class ReadLockingInputStream
+    private static class ReadLockingInputStream
         extends WrappingInputStream
     {
         private volatile RepositoryItemUidLock lock;