Use lioadm as iscsi helper on RHEL 7

On RHEL 7 it is necessary to use lioadm as iscsi_helper. This patch handles
proper configuration and appropriate package installation.

Change-Id: Ic3a41015c95f0b5f394d0c4b58dfc0eb10d5037d
Merge "Use lioadm as iscsi helper on RHEL 7"