gh-1358 Roxie memory leaks
gh-1358 Roxie memory leaks

Complete the ping-related fixes - messages snet in response to ping
are not acknowledged and should not be saved in the retry buffer.

Fixes gh-1358.

Signed-off-by: Richard Chapman <5900d56196fe29dba8e3ae556d57eae28e9f0195@hpccsystems.com>

afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform,afishbeck/HPCC-Platform