1.Upgrade pylint to 2.4.4, add exclusions to the tests, and
fix some lint errors in the code
2. Fix user creation with GRANT in MySQL 8.0(Ubuntu Focal)
In Ubuntu Bionic (18.04) mysql 5.7 version used to create
the user implicitly when using using the GRANT.
Ubuntu Focal (20.04) has mysql 8.0 and with mysql 8.0 there
is no implicit user creation with GRANT. We need to
create the user first before using GRANT command.
See also commit I97b0dcbb88c6ef7c22e3c55970211bed792bbd0d
3. Remove fwaas from the zuul.yaml
4. Remove DB migration test which is failing ue to FWaaS migration
5. Fix cover tests python version in .tox
6. fix requirememnts