Read environments from Tenant instead of Config Map

[ebaron]

The current Deployments API queries environments from the fabric8-environments Config Map [1]. This Config Map does not support more complex scenarios such as namespaces that reside on another cluster or those shared within an organization (#350). Instead of using fabric8-environments, we should read environments from Tenant with the /api/user/services endpoint.

[1] https://github.com/fabric8-services/fabric8-tenant-team/blob/106ef4cb92dee51e0c7d09a5dbd7f96e2c7435f2/packages/fabric8-tenant-team/src/main/fabric8/fabric8-environments-cm.yml

[stooke]

The deployments code currently caches /api/user/services for the duration of the current request, so this would indeed be more efficient.