client: RPC Client: Delay the deletion of the boost::asio socket and...

client: RPC Client: Delay the deletion of the boost::asio socket and ssl::stream object. This fixes issue 281. In newer boost (?) versions, boost::asio tries to write to the socket after the SSL stream and the socket was shutdown. Therefore, we have to delay the deletion and hope that no segmentation fault is triggered. The correct way would have been to use a shared_ptr for the socket. However, we decided to avoid using shared_ptr in the RPC client component for now.