bump kafka module version

bump kafka version to 1.6.9

update version to 1.6.8

update version to 1.6.7

publish package on push

patch: fix potential use after free

rd_kafka_topic_partition_list_query_leaders_async_worker() can
free rko->rko_u.leaders.eonce by calling rd_kafka_enq_once_del_source().
After use this object again:

if (rko->rko_u.leaders.eonce) {
        rd_kafka_enq_once_disable(rko->rko_u.leaders.eonce);
        rko->rko_u.leaders.eonce = NULL;
}

This patch adds to rd_kafka_enq_once_del_source() a
return indication that the object has been freed.

Closes tarantool/security#94

Update CMakeLists.txt

patch: fix use after free in rdhttp.c

Fix macos build

Add missing include file

To fix build after Tarantool update.