[Vanilla] Added unit test on get_hadoop_ssh_keys method
[Vanilla] Added unit test on get_hadoop_ssh_keys method

Change-Id: Ib096982f4e154d5ddb5b7bb19a177b023967f7e8

redhat-openstack/sahara,matips/iosr-2015,bigfootproject/sahara,xme1226/sahara,bigfootproject/sahara,esikachev/scenario,mapr/sahara,redhat-openstack/sahara,zhujzhuo/Sahara,redhat-openstack/sahara,tellesnobrega/sahara,citrix-openstack-build/sahara,egafford/sahara,citrix-openstack-build/sahara,openstack/sahara,xme1226/sahara,egafford/sahara,crobby/sahara,henaras/sahara,ekasitk/sahara,matips/iosr-2015,keedio/sahara,openstack/sahara,zhangjunli177/sahara,esikachev/scenario,tellesnobrega/storm_plugin,ekasitk/sahara,zhangjunli177/sahara,zhujzhuo/Sahara,esikachev/sahara-backup,tellesnobrega/sahara,esikachev/scenario,esikachev/sahara-backup,citrix-openstack-build/sahara,zhangjunli177/sahara,henaras/sahara,tellesnobrega/storm_plugin,zhujzhuo/Sahara,crobby/sahara,matips/iosr-2015,crobby/sahara,mapr/sahara,keedio/sahara,keedio/sahara,mapr/sahara,esikachev/sahara-backup,tellesnobrega/storm_plugin,xme1226/sahara,henaras/sahara,ekasitk/sahara,bigfootproject/sahara