Fix connectors build.
Fix connectors build.

- reference connectors versions from versions.bzl
- add snapshot repository to pom.xml (needed for JUnit 4.13-SNAPSHOT)

	Change on 2018/03/02 by idv <idv@google.com>

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=187621870

GoogleCloudDataproc/hadoop-connectors,GoogleCloudDataproc/hadoop-connectors