Add support for negative tests with admin client
Add support for negative tests with admin client

This adds the missing support for admin clients and implements an
example based on flavor creation. Instead of listing all result code
checks it is now possible to define on default.

Change-Id: I9512c1b91eb227e35faf24e3e88ed73a6ed3b734
Partially-implements: bp autogen-negative-tests

varunarya10/tempest-lib,cneill/tempest-lib,afaheem88/tempest-lib,JioCloud/tempest-lib,sorenh/tempest-lib,mtreinish/tempest-lib