global shutdown hooks to free global resources once

If plugins use 3rd party libs like openssl, they may have to call cleanup functions that should only be called once and with a mutex.

The chassis should get a hash of { string, cleanup_func } which are called on shutdown. In the case of openssl we would register code that would call:

        curl_global_cleanup();

        SSL_free_comp_methods();
        ERR_free_strings();
        ENGINE_cleanup();
        CRYPTO_cleanup_all_ex_data();