HBASE-7942. Makes the RegionServer aware of favored-nodes. The regionserver can now specify where to create the region files if the underlying HDFS supports the corresponding create(..favorednodes..) API.

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1485584 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HBASE-8559-trunk-gd