supervisor.exec_config only returns completion deferred - no tests

job id is created and manged by _Job.
Create mocked group
Add retrying create server and tests for such - can only retry if the find_server call suceeded and returns None
Fix after rebasing based on part 1
Fix the _get_erver_info helper function in the tests for the nova launch worker
Use urlencode and urlunsplit rather than quote/unquote and string interpolation
Add a bunch of docstrings in the inner functions in create_server
Replace confusing and wrong lambda with an explicitly defined function
Change the metadata default assignment
adding to pool from job caller - no tests

After discussing with @cyli, we decided to change pool addition in this
branch itself. Now, all the callers of _Job and _DeleteJob will get
deferred and will add it to the pool
Merge branch 'master' into as-284-check-for-server-on-nova-error-part2

Conflicts:
	otter/test/test_retry.py
	otter/test/worker/test_launch_server_v1.py
	otter/worker/launch_server_v1.py
Remove some old usages of failureResultOf
started tests
DeferredPool has __contains__
Merge branch 'master' into as-284-check-for-server-on-nova-error-part2
execute_launch_config shorter tests

using FakeSupervisor and FakeJob
supervisor lint fixes
Merge branch 'master' into job-synchronous

Conflicts:
	otter/test/test_supervisor.py
Inject treq into create_server so that StubTreq can be used to test it
Inject _treq into check_success too