Don't do signing in staging, emit progress fedmsgs to stg bus

[jlebon]

There is no staging Robosignatory anymore and we should avoid using the production one for staging builds. We can still submit progress messages (build.state.chage) but it should be to the staging bus, not prod.

[dustymabe]

We should probably check what jenkins we are on and automatically not do it (just in case someone created the wrong secret in the staging pipeline).