`rustls::ConnectionCommon::complete_io` could fall into an infinite loop based on network input

If a close_notify alert is received during a handshake, complete_io
does not terminate.

Callers which do not call complete_io are not affected.

rustls-tokio and rustls-ffi do not call complete_io
and are not affected.

rustls::Stream and rustls::StreamOwned types use
complete_io and are affected.