This commit adds two new tox environments for bandit scanner. To run any
of them you can use tox commands:

1) 'tox -e bandit' to run bandit scanner against all the code
2) 'tox -e bandit-baseline' to run bandit scanner only against the last
commit or the current changes.

Bandit job uses 'bandit-baseline' tox environment to veryfy that no new
issues were introduced.

Change-Id: I1fc3bb0d5d151f215b9efc916f921fabaa72e7d8