TestNotesMigration: Always set values in setFromEnv

AbstractDaemonTest#beforeTest calls setFromEnv to set up its migration
state prior to running any tests. We were accidentally failing to
clear the migration bits when NoteDb is disabled. This led to possible
nondeterministic failures if the body of the test modifies the
migration state, as happens in ChangeRebuilderIT.

Change-Id: If674b2ac48a456c2d7971ab4024e2b8c06d7b198

gerrit-server/src/test/java/com/google/gerrit/testutil/TestNotesMigration.java

@@ -81,6 +81,8 @@ public class TestNotesMigration extends NotesMigration {
       case CHECK:
       case OFF:
       default:
+        setWriteChanges(false);
+        setReadChanges(false);
         break;
     }
     return this;