Add an allocator test for preinit task object
Add an allocator test for preinit task object

Add a specific test case to test allocation of a task which is already
in store and has no network attachments created before allocator is run.

Signed-off-by: Jana Radhakrishnan <045898bda7d4800fe4909a9831e702ab79e266be@docker.com>

aaronlehmann/swarmkit,sungwonh/swarmkit,dperny/swarmkit-1,AliyunContainerService/swarmkit,vasil-yordanov/swarmkit,alyyousuf7/swarmkit,jlhawn/swarmkit,Noyan759/swarmkit,yongtang/swarmkit,fate-grand-order/swarmkit,cheyang/swarmkit,cezarsa/swarmkit,alyyousuf7/swarmkit,allencloud/swarmkit,docker/swarmkit,RenaudWasTaken/swarmkit,elifa/swarmkit,sungwonh/swarmkit,yongtang/swarmkit,allencloud/swarmkit,elifa/swarmkit,AliyunContainerService/swarmkit,docker/swarmkit,Noyan759/swarmkit,deljuven/swarmkit,diogomonica/swarmkit,deljuven/swarmkit,cezarsa/swarmkit,jlhawn/swarmkit,dperny/swarmkit-1,aaronlehmann/swarmkit,cheyang/swarmkit,vasil-yordanov/swarmkit,fate-grand-order/swarmkit,RenaudWasTaken/swarmkit,diogomonica/swarmkit