The take_action() function was calling get_agent() with the wrong
attribute, causing agent deletion to fail. It turns out calling
get_agent() isn't necessary; this removes the call entirely and moves
the 'ignore_missing' argument to the delete_agent() function.
Change-Id: Iaa3754a3be0765112f396495fa5fb2e32e6eae4e
Closes-Bug: #1711301