Don't quit debugger when the program terminates, only after `quit`.

tests/debugger/frame_restart_test.dart

 // Copyright (c) 2015, the Dartino project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
-// DartinoDebuggerCommands=b breakHere,r,bt,f 5,restart,bt,f 11,restart,bt,d 0,f 3,restart
+// DartinoDebuggerCommands=b breakHere,r,bt,f 5,restart,bt,f 11,restart,bt,d 0,f 3,restart,q
 
 void breakHere() {}
 
 void foo(int i) {
   print(i);
   if (i == 0) {
     breakHere();
   } else if (i > 5) {
     var local = i + 1;
     foo(i - 1);
   } else if (i > 3) {
     var local = i + 1;
     var local2 = i + 2;
     foo(i - 1);
   } else {
     foo(i - 1);
   }
 }
 
 void main() {
   foo(10);
 }