Wait for HDFS readiness after datanode services start

Bug #1240511 consists of two connected problems:
1. oozie-setup.sh exists with status code 0 when error occurs.
2. Savanna expects that HDFS is running immediately
   after "/usr/sbin/hadoop-daemon.sh start datanode" execution

This patch addresses the second issue.
The first issue is addressed by https://review.openstack.org/#/c/62511/

Added check that all datanodes are running before manipulations with HDFS.

Fixes bug #1240511

Change-Id: I953512e2b430fba562ee3dceb8c1781aa8ad61bf
Merge "Wait for HDFS readiness after datanode services start"