pkg/auth/badgerauth: silence ErrNoRewrite in gcValueLog

This change modifies gcValueLog so that it won't alarm typical users
that something's wrong when ErrNoRewrite is actually expected (other
codebases using BadgerDB also silence ErrNoRewrite for this purpose).

Change-Id: I742edea063439f194b061b82e8ed8c6dd492b39c

pkg/auth/badgerauth/db.go

@@ -126,7 +126,10 @@ func (db *DB) gcValueLog(ctx context.Context) (err error) {
 		case <-ctx.Done():
 			err = ctx.Err()
 		default:
-			err = db.db.RunValueLogGC(0.5)
+			// Run GC and optionally silence ErrNoRewrite errors:
+			if err = db.db.RunValueLogGC(.5); errs.Is(err, badger.ErrNoRewrite) {
+				err = nil
+			}
 		}
 		gcFinished(&err)
 	}