Kill tasks

[ronin1]

I Added 2 new flags:

• --kill-tasks: kill all related ecs tasks and deregister current task definition for the service so the new tasks can start. This is useful if auto scaling is enabled & minimum task count is on. It allows for unattended deployment.
• --no-kill-tasks: is actually on by default and does not deregister or kill existing tasks. This is currently the behavior before this pull request.
• remove most python linter warnings

Tested this on my own CodeFresh build & it is working awesome