Work around default parameter problem in the static analyzer.

In cases like:
  struct C { ~C(); }
  void f(C c = C());
  void t() {
    f();
  }

We currently do not add the CXXBindTemporaryExpr for the temporary (the
code mentions that as the default parameter expressions are owned by
the declaration, we'd otherwise add the same expression multiple times),
but we add the temporary destructor pointing to the CXXBindTemporaryExpr.
We need to fix that before we can re-enable the assertion.