Fix kafka consumer not destroyed in close

[ikeberlein]

Not destroying underlying kafka consumer in close() method leads to unclean librdkafka shutdown and very often to segfaults.

[arnaud-lb]

Normally the rk handle is destroyed when the KafkaConsumer object itself is destroyed, so I don't think we need to close it explicitly here. However maybe we don't destroy various resources in the right order when the rk is closed later?

Do you have a reproducer?

[plehatron]

Hey @arnaud-lb, I prepared and reported the reproducer in #571. The issue includes details about the bug this PR fixes.

[mattiabasone]

Hey! Do you happen to have any news on this @arnaud-lb?
I'm experiencing the same issue during PHPUnit tests. In the CI, I'm using Ubuntu 24.04 and the shivammathur/setup-php GitHub action for setting up the environment with PHP 8.3.25 and rdkafka 6.0.5

[takeit]

@arnaud-lb same issue here, could this be merged, pls? it's been over 2 years for 1 line to be merged