High RSS memory usage due to MADV settings

In versions of Packetbeat prior to 7.10.2, the go runtime defaults to MADV_FREE by default. In some cases, this can lead to high RSS memory usage while the kernel waits to reclaim any pages assigned to Packetbeat. On versions prior to 7.10.2, set the GODEBUG="madvdontneed=1" environment variable if you run into RSS usage issues.