Fix approval copying when labels are set on push

A primary key error was occurring whenever a PatchSet was pushed
with a label overriding a sticky approval from a prior PatchSet.
The cause is that when changes are read from NoteDb, ApprovalCopier
doesn't have access to these new approvals.

This change adds an optional parameter to ApprovalCopier#copy,
dontCopy, which is used to block copying of approvals of the
given (account, label) pairs from any prior PatchSets.

Change-Id: I417deba5b42e38f498c879696998651597535659

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/git/AbstractPushForReview.java

@@ -783,6 +783,23 @@ public abstract class AbstractPushForReview extends AbstractDaemonTest {
     pushWithReviewerInFooter("Notauser", null);
   }
 
+  @Test
+  public void pushNewPatchsetOverridingStickyLabel() throws Exception {
+    ProjectConfig cfg = projectCache.checkedGet(project).getConfig();
+    LabelType codeReview = Util.codeReview();
+    codeReview.setCopyMaxScore(true);
+    cfg.getLabelSections().put(codeReview.getName(), codeReview);
+    saveProjectConfig(cfg);
+
+    PushOneCommit.Result r = pushTo("refs/for/master%l=Code-Review+2");
+    r.assertOkStatus();
+    PushOneCommit push =
+        pushFactory.create(db, admin.getIdent(), testRepo, PushOneCommit.SUBJECT,
+            "b.txt", "anotherContent", r.getChangeId());
+    r = push.to("refs/for/master%l=Code-Review+1");
+    r.assertOkStatus();
+  }
+
   private void pushWithReviewerInFooter(String nameEmail,
       TestAccount expectedReviewer) throws Exception {
     int n = 5;