Bump default Hadoop version to 2.2.0. (This is already the dependency version reported by published Maven artifacts.) See JIRA for further discussion.

Author: Sean Owen <sowen@cloudera.com>

Closes #5027 from srowen/SPARK-5134 and squashes the following commits:

acbee14 [Sean Owen] Bump default Hadoop version to 2.2.0. (This is already the dependency version reported by published Maven artifacts.)