Maid 22 bad alloc

https://maidsafe.atlassian.net/browse/MAID-22

the verification involves using routing_node network across droplets

it may worth to check whether the routing_node network (using next branch) suffers the same issue as using interim_merge_of_unsafe_packet_loss_tolerance branch.
If not, then no need to merge this MAID-22_bad_alloc branch into next.

The *Socket fetched from connection_manager turns out to be pointing to a socket instance that may got destructed by another thread, during the period of HandleReceiveFrom function call.