remove extra redis and move to using built images for examples

[dcmcand]

Fixes #616 Fixes #617 Part of #599

Description

Updates docker-compose files in examples directory

This pull request:

• removes extra redis instance from examples/docker/docker-compose.yaml
• sets conda-store-worker and conda-store-server to use quansight/conda-store-server in examples/docker/docker-compose.yaml
• sets conda-store-worker and conda-store-server to use quansight/conda-store-server in examples/docker-without-nfs/docker-compose.yaml

Pull request checklist

• [X] Did you test this change locally?
• [ ] Did you update the documentation (if required)?
• [ ] Did you add/update relevant tests for this change (if required)?

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[costrouc]

@dcmcand I'll be honest this is a set of examples I haven't tested in a LONG time. Actually all of the examples haven't been tested in awhile. The docker-compose.yaml in the root of the repository is the most tested.

Should we be testing examples?

[dcmcand]

I think that examples should be tested. I know when I start using a new project, I often use the example as a getting started place. If they aren't tested and don't work, that would be pretty frustrating.