Allow for small window where state is pending but bodhi composes updates

[nirik]

Right now, once we have a go on a RC compose, we change bodhi config:

1. state from pending to stable
2. stable tag from f32 to f32-updates
3. composed by bodhi from False to True.

However, this messes up using bodhi as a source for truth as to when something is stable/released.

So, ideally I would like to be able to do just 2 and 3 before the release, and compose and push updates repos from bodhi as today, but leave the state in 'pending' until the actual real release day. Then we change it over to 'stable'.

I am not sure what checks for that state, but we would need to make sure it doesn't use it for deciding if it should compose or what tag it's putting updates in.