CLOUDIFY-1535 Fixed wrong import of Objects class.
CLOUDIFY-1535 Maintain zookeeper session id.

- Added session id to zookeeper session logs.
- Added zookeeper session disconnected/expired test.
- Run an embedded zookeeper server instead of using an external process for unit tests.
- Disable org.apache.zookeeper logs for unit tests.
Merge branch 'develop' of https://github.com/CloudifySource/cosmo-leader into develop