unit test fix for #3052 and #3053

@mdogan 

As I understood, it waits for currently active migrations. I am thinking that after shutdown of this node, there can be other started migrations (not active right now, will be active after shutdown). For example backup count of that map can be 2 and one backup of that map may be this node. After this node shutdown, a new node must be selected to be a backup of that map by migrating from other backup node and there will be an active partitioning/migration. Is this case is wrong for Hazelcast or just for this issue ?

My explanation may be so confused :) so I hope that I could understand what I am thinking about this issue :)