Clean up redundant code constructs

Results of the following IntelliJ inspections:
 * Redundant 'isInstance' or 'cast' call
 * Redundant array creation
 * Redundant Collection operation
 * Redundant String operation
 * Redundant type cast

The only manual change was to remove a suppression and comment about a
redundant cast which doesn't appear to be an issue in the current
version of JDK 8

Change-Id: I34a70d436512cc4efe9dafb0917be3dfce4ba06b

java/com/google/gerrit/server/IdentifiedUser.java

@@ -96,13 +96,13 @@ public class IdentifiedUser extends CurrentUser {
           accountCache,
           groupBackend,
           disableReverseDnsLookup,
-          Providers.of((SocketAddress) null),
+          Providers.of(null),
           state,
           null);
     }
 
     public IdentifiedUser create(Account.Id id) {
-      return create((SocketAddress) null, id);
+      return create(null, id);
     }
 
     public IdentifiedUser create(SocketAddress remotePeer, Account.Id id) {