cdh plugin yum install option "-y" missing
cdh plugin yum install option "-y" missing

when I install cdh using sahara with CentOS image,
it occurs timeout exception because of missing option "-y".

Change-Id: Iee9a5d6ab7868fc426c6a82bc7a45228680f8cc6
Closes-Bug: #1566278

egafford/sahara,tellesnobrega/sahara,tellesnobrega/sahara,egafford/sahara,openstack/sahara,openstack/sahara