Remove a datacenter from routing without reharvesting

[damb]

Hi,

I'm not sure if this feature is already in place (I also didn't have a look into the code yet).
However, it would be nice to have the possibility to remove a datacenter from routing

• without reharvesting
• without manual interaction of the concerning datacenter i.e. removing the datacenter's localconfig manually.

For exemplary use cases, see e.g. EIDA/userfeedback#88.