VehSpawner: Fix Advanced Logistics blocking static weapon respawns.

[dijksterhuis]

When an advanced logistics container vehicle is destroyed, static weapons created by the vehicle spawner (vehicle asset manager) system can be blocked from respawning.

The static weapon object is still alive, hidden and attached to the player who loaded it into the now destroyed container vehicle... meaning the static weapon will not respawn at the vehicle spawn point.

This change fixes the block on spawning by checking if the spawn point's _currentVehicle was loaded into a container vehicle with advanced logistics, and whether the container vehicle is still alive. If not, force respawn of _currentVehicle.

additional

_vehicle getVariable ["log_inventory_loaded", false] should hopefully double up as a check for whether the advanced logistics module is enabled -- variable should not be set otherwise.

Would be nice to unload static weapons from a destroyed adv-log container vehicle if they are configured for WRECK. but that's more complex.

Tested this pretty thoroughly, not encountered any issues.

[dijksterhuis]

will need updating if #209 is merged first (and vice versa).