If user wants to show the nodes which are already deleted they
can use '-D' in node-list, but if '-D' is not set, 'show_deleted'
column should not shown in node-list. 'show_deleted' option should
always be True/False, not None.
Change-Id: I83ace7515f31bcb30c83b9f0147f33dd94c72baf
Closes-bug: #1526177
2c525e9178