Test using mysql + postgres if available

If mysql is avaiable via the standard testing user
'openstack_citest' with password 'openstack_citest'
then attempt to setup mysql or postgres and use
those databases for the duration of the test.

Adjust the tox template to include the two main mysql
library variants [MySQL-python, PyMySQL] and the psycopg2
postgres library so that these new tests will find the
appropriate library (sqlalchemy will attempt to find
these when connecting).

Change-Id: I90e59504663277d277d94e1f2a11031119bcedd6
Doc strings and comments clean-up

* Added missing period for doc strings
* Correct syntax errors
* Remove H402 from flake8 ignore list

Change-Id: Ia8592bf99378e3658d6cca2ceb148bf9eb0b5de8
Added more unit tests for Task and FunctorTask

* More tests were added for task.Task and task.FunctorTask
  to enhance code coverage.

Change-Id: Idacf0ee3fcb84d71cdb57d4f6d986f7e983597f0
Merge "Added more unit tests for Task and FunctorTask"
Merge "Test using mysql + postgres if available"