registry `make` commands aren't quiet

[torgeirl]

The make start-registry and make stop-registry commands added in #18 aren't quiet.

1. After the start command has finished, it is followed by some debug print we aren't interested in:

$ time="2023-03-14T08:52:52.451169715Z" level=info msg="Starting upload purge in 23m0s" go.version=go1.16.15 instance.id=d73f1b7c-0ab6-4a94-a98f-bd710cbb1332 service=registry version="v2.8.1+unknown" 
time="2023-03-14T08:52:52.451001494Z" level=warning msg="No HTTP secret provided - generated random secret. This may cause problems with uploads if multiple registries are behind a load-balancer. To provide a shared secret, fill in http.secret in the configuration file or set the REGISTRY_HTTP_SECRET environment variable." go.version=go1.16.15 instance.id=d73f1b7c-0ab6-4a94-a98f-bd710cbb1332 service=registry version="v2.8.1+unknown" 
time="2023-03-14T08:52:52.451526808Z" level=info msg="redis not configured" go.version=go1.16.15 instance.id=d73f1b7c-0ab6-4a94-a98f-bd710cbb1332 service=registry version="v2.8.1+unknown" 
time="2023-03-14T08:52:52.465950105Z" level=info msg="using inmemory blob descriptor cache" go.version=go1.16.15 instance.id=d73f1b7c-0ab6-4a94-a98f-bd710cbb1332 service=registry version="v2.8.1+unknown" 
time="2023-03-14T08:52:52.466645677Z" level=info msg="listening on [::]:5000" go.version=go1.16.15 instance.id=d73f1b7c-0ab6-4a94-a98f-bd710cbb1332 service=registry version="v2.8.1+unknown"

This has to be exited manually (CTRL-C). It's caused by the registry container's log level defaulting to debug. Not sure how it can be adjusted.

2. The stop command works, but isn't graceful and it too has to be exited manually.