[AGENT++] [AGENTX++] Concurrency problem in masteragent

[Arne Albrecht]

Hi there,

i think i found a bug in the AgentX++/Agent++ code:
If a request affects two subagents and the response of these agents return
quite at the same time,
the masteragent might crash.
If the two response threads pass MasterAgentXMib::process_ax_response() and
finish, they both call MIB::finalize() -
but the second thread will enter with an invalid pointer.

A quick and dirty solution: keep the access to the RequestList syncronized
until the process_ax_response() method exits.
This seems to work, but cause recursive-locking warnings.

Regards,
    Arne