This change makes the etcd package compatible with the existing Go
ecosystem for module versioning.
Used this tool to update package imports:
https://github.com/KSubedi/gomove
Some goroutines in test functions will be leaked in certain cases.
This patch stops these leaks no matter what happens in test, by
putting the blocking channel in select together with a new stopc
channel, or adding 1 buffer to the blocking channel.
Adding integration test TestTransferLeadershipWithLearner, which ensures
that TransferLeadership does not timeout due to learner is automatically
picked by leader as transferee.
Brandon Philips