Background Memory Attack: Unable to wait for memory to be fully consumed

[Simon Tabor]

As the BG memory attack is forking into a new process, it currently doesn't allow waiting for the process to complete.

Even though the memory attack is synchronous, as we've forked the process, the main event loop isn't interrupted and could easily have stopped the attack before the sync process has completed filling the memory.

Note: I don't think this impacts the BG CPU attack as it will immediately cause the CPU increase