Fixed these tests :
1.TestNetworkDBIslands
Addresses : https://github.com/docker/libnetwork/issues/2402
2.TestNetworkDBCRUDMediumCluster
Addresses : https://github.com/docker/libnetwork/issues/2401
By :
1. Importing gotest.tools/poll to use poll.WaitOn
Above function can be used to check a condition at regular intervals
until a timeout is reached
2. Replacing Sleep with poll.WaitOn
2. Adding closeNetworkDBInstances to close remaining DBs
Signed-off-by: Arko Dasgupta <arko.dasgupta@docker.com>
34a636bf51