warn that concurrent SSL connections won't work

[hithwen]

From IBM documentation https://www.ibm.com/docs/en/ibm-mq/9.0?topic=applications-secure-connections-mq-queue-manager

If you use the IBM WebSphere MQ 6.0 and later client libraries, then you can create a SSL connection only if you close any previous SSL connection first. Multiple concurrent SSL connections from the same process to the same or different queue managers are not permitted. If you attempt more than one request, you get the warning MQRC_SSL_ALREADY_INITIALIZED, which might mean that some requested parameters for the SSL connection were ignored.

[codecov[bot]]

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