Lifetime issues with static instances of ZMQ manager and Application on unexpected doocs server shutdown

[phako]

If the DOOCS server has a problem (e.g. rpcbind not running, type of variable with history has changed) the destruction order of the static variables in the server causes issues.

It seems that the ZMQSubscriptionManager singleton is destroyed first, causing either:

• An incoming ZMQ callback to crash because the accessors have not unsubscribed themselves yet
• A crash in the accessor unsubscribe call because the ZMQSubscriptionManager is already dead

This is only an issue in non-standard exit situations of the server. Orderly shutdown of the doocs server (SIGTERM/INT) works fine.

[mhier]

Note: This probably has to be solved on a deeper level in ControlSystemAdapter and/or ApplicationCore. Hence I will mark this as a umbrella ticket.