Add cases for iscsi_direct flag
    
    Flag: VIR_CONNECT_LIST_STORAGE_POOLS_ISCSI_DIRECT
    
    Change-Id: I4d4c4c3ad73af5e3f6e00ba01ca6913ff40a890c
    Signed-off-by: Liping Cheng <lcheng@redhat.com>
    Reviewed-on: https://code.engineering.redhat.com/gerrit/181586
    Tested-by: Libvirt Jenkins <libvirt-jenkins@redhat.com>
    Signed-off-by: Liping Cheng <lcheng@redhat.com>