Set self.kwargs in horizon.tables.actions.LinkAction

Set self.kwargs during __init__ so that get_link_url no longer raises
an AttributeError at "return self.url(datum, **self.kwargs)".

Change-Id: I97aeab781ee1945c3028590be0a6a046c7fcd9b9
Closes-Bug: 1290909
Merge "Set self.kwargs in horizon.tables.actions.LinkAction"