apps depend on this.
- Don't release IRpcProxyBuffer on ifproxy destruction - the caller
  will do this for us.
- Make find_proxy_manager add a reference to the proxy manager and
  make proxy_manager_construct return an object with a valid
  ref-count.
- Remove stray not operator to fix a memory leak / crash in
  proxy_manager_destroy.
- More debug messages, especially on errors.
- Fix ref-count leak in the Class Factory proxy.
- Add a test case for IClassFactory_CreateInstance.