HELIX-89: User added listeners are not re-init after zk session expiry
HELIX-89: User added listeners are not re-init after zk session expiry
HELIX-91: missing retry logic in zkclient
[HELIX-92] Adding service discovery recipe
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-helix