Fix the dev playbook

Hi Sergey, thanks for the playbooks. I was interested in getting the `dev.yml` to run to get the ports going. I fixed a few things:
1. Removed the `tasks` dictionary  (you don't need it in roles)
2. Made use of the `mirror` variable
3. Removed the duplicate `adjust installpath` task since the `dev.yml` playbook includes the `common` role.

You might want to repeat (1) with your other roles, I just didn't want to take over your git history hehe.