Fix SSLSocketInitiator fd leak and CPU spin on connection failure (#713)

Three related bugs caused file descriptor leaks and busy-spinning when
the SSL initiator cannot connect (e.g. dead port):

1. ssl_socket_close() skipped socket_close() when an SSL object was
   present, relying on SSL_free() to close the fd. But the BIO is
   created with BIO_NOCLOSE in SSLSocketInitiator::doConnect, so
   SSL_free() never closes the underlying fd. Add socket_close() after
   the SSL_shutdown loop so the fd is always released.

2. ConnectorWrapper::onError() (connection-refused / POLLERR path) did
   not drop the socket from the monitor before notifying the strategy.
   On each subsequent block() call poll() returned POLLERR again,
   spinning the CPU. Add monitor.drop(socket) first, matching the
   pattern in ServerWrapper::onError.

3. handshakeSSLAndHandleConnection() deleted the SSLSocketConnection on
   SSL handshake failure without first calling disconnect(), leaving the
   socket in the monitor's read set. Call pSocketConnection->disconnect()
   before pSession->disconnect() so the specific failing socket is
   removed from the monitor immediately.

Fixes #682.