Strip trailing dot off hostname used for SSL validation.

[wbarnha]

When using FQDN's with trailing dots to connect to a broker, the trailing dot in the hostname should be stripped before using the hostname for validation against the server's certificate.

For instance, this code:

producer = KafkaProducer(
        bootstrap_servers="redpanda.redpanda.svc.cluster.local.:9093",
        security_protocol="SSL",
)

Will cause certificate validation to fail when the subject name doesn't contain the trailing dot.

For some context, this is also a problem with librdkafka: confluentinc/librdkafka#4348

The current stance from the OpenSSL team is this is an application layer issue: openssl/openssl#11560

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