This allows the server delete command to wait for the server to be
deleted (obviously).
The wait method is the same model that Tempest uses, i.e. wait for a 404
on server GET (successful deletion), fail if the server went to ERROR
status, or fail if a timeout is reached. The default timeout of 300
seconds is also what Tempest uses.
Closes-Bug: #1460112
Change-Id: I0e66c400903e82832944d1cad61e7eb30177c3e8