NoteDbUpdateManager: Default checkExpectedState to true

This was always the intention, as it's the safest approach.
Unfortunately, since this was dead code, flipping the flag found a bug
in the logic.

We don't want to check whether the expected state matches using the
ChainedReceiveCommands, which includes the results of any updates
we're about to apply--of course that won't match. Instead, reach in
and grab the underlying RepoRefCache. This continues avoiding an extra
read, since it uses the same cached ref value. Using a cached value
here should still be safe as the ReceiveCommand itself will fail if
the ref was updated in the meantime.

Change-Id: I8bc6b1706f27c31e2ca335910040fe083bf146e8

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

@@ -49,6 +49,10 @@ public class ChainedReceiveCommands implements RefCache {
     this.refCache = checkNotNull(refCache);
   }
 
+  public RepoRefCache getRepoRefCache() {
+    return refCache;
+  }
+
   public boolean isEmpty() {
     return commands.isEmpty();
   }

gerrit-server/src/main/java/com/google/gerrit/server/notedb/NoteDbUpdateManager.java

@@ -180,7 +180,7 @@ public class NoteDbUpdateManager {
   private OpenRepo changeRepo;
   private OpenRepo allUsersRepo;
   private Map<Change.Id, StagedResult> staged;
-  private boolean checkExpectedState;
+  private boolean checkExpectedState = true;
 
   @AssistedInject
   NoteDbUpdateManager(GitRepositoryManager repoManager,
@@ -486,7 +486,7 @@ public class NoteDbUpdateManager {
         continue;
       }
 
-      if (!expectedState.isChangeUpToDate(changeRepo.cmds)) {
+      if (!expectedState.isChangeUpToDate(changeRepo.cmds.getRepoRefCache())) {
         throw new OrmConcurrencyException(String.format(
             "cannot apply NoteDb updates for change %s;"
             + " change meta ref does not match %s",
@@ -504,7 +504,7 @@ public class NoteDbUpdateManager {
 
       Account.Id accountId = u.getAccountId();
       if (!expectedState.areDraftsUpToDate(
-          allUsersRepo.cmds, accountId)) {
+          allUsersRepo.cmds.getRepoRefCache(), accountId)) {
         throw new OrmConcurrencyException(String.format(
             "cannot apply NoteDb updates for change %s;"
             + " draft ref for account %s does not match %s",