HBASE-13339 Update default Hadoop version to 2.6.0
HBASE-13339 Update default Hadoop version to 2.6.0

ibmsoe/hbase,ibmsoe/hbase,ibmsoe/hbase,ibmsoe/hbase,ibmsoe/hbase,ibmsoe/hbase,ibmsoe/hbase,ibmsoe/hbase,ibmsoe/hbase,ibmsoe/hbase