The set --property command requires that the input match
the "key=value" type, but if the type don't match, the return
value will be None, and the command still can be implemented
successfully, this may confuse the users. I think we should
raise exception if the argument type don't match "key=value".
So I make some changes in KeyValueAction class in this patch.
Change-Id: If4a00ae6da08bc12362ef2fc82012b42839141f0
