Fix use of nonexistent class variable in accounts

This commit fixes cases in tempest.common.accounts cases where some
methods were attempting to use non-existent class level variables.
It also improves the get_hash methods and calls to remove_hash.

Co-Authored-By: Andrea Frittoli <andrea.frittoli@hp.com>
Change-Id: I30cf59b981e0db3a3e50357a8db489519767c0ca
Merge "Fix use of nonexistent class variable in accounts"