Clean up Sentry pillar configuration
Both nginx and containers SLS rely on the keys in docker_containers
pillar entry to select what items to provision.
As such, we need to rename one of the service into 'sentry'
(an alternative was to rename files to sentry_web).
This is a follow-up for 52ed226f98f8.
Reviewed By: dereckson
Maniphest Tasks: T1360
Differential Revision: https://devcentral.nasqueron.org/D2005