Implement DeferredPool, which will be used to wait on certain deferreds to prevent shutdown
Add a deferredpool to supervisor
Delay shutdown until supervisor jobs are done
Add a comment explaining why the supervisor service works
Document coiterate ivar in supervisor
Started AUTO-561, validating launch config

Started the implementation. Tests still remaining.
added validate_launch_config tests
Tests for validate_image added

Implemented mock_treq that mocks treq with given arguments
moved from json_schema/ to worker/
Adjusted validate tests after moving to worker

- Modified supervisor and rest/* for worker change
- Yet to add tests for supervisor changes
Works with REST APIs

Tested create group and edit launch config. Works with valid and invalid data
patch supervisor calls in unitgration tests
launch_server type check
path fix after worker move
Adding review comment and empty tests for supervisor
completed tests for supervisor and validate_config.py
changes to client and models
Merge branch 'master' into maas-policies
maas policy behavior added
test for create maas policy