#22 5.1.2-p02: duplicate registration segfault; memory leaks

[Robert Story]

This patch fixes:

1) a known segfault when an old_api hander is
registered with a duplicate OID.
2) a potential segfault for a failed registration of an
AgentX subagent which is not attachted to the master agent
3) potential memory leaks when a registration fails

[Robert Story]

official patch 2 for 5.1.2