Cleanup fde data members before memset in fde::clean() corrupts their state.

Cleanup fde data members before memset in fde::clean() corrupts their state.
This prevents fde::timeoutHandler and fde::closeHandler memory leaks but there
will probably be more corruption as fde data members are added or changed.

Made fde::clean() private to prevent it from spreading through the code.
Use a new fde object to clean an old one, for now.