This patch served for a manual testing counterpart for osmo-bsc to implement
MSC pooling.
This enables a basic MSC pooling setup, but for a production setup, osmo-msc
would still lack various features related to unloading subscribers to another
MSC as explained in 3GPP TS 23.236.
Change-Id: Iafe0878a0a2c8669080d757b34a398ea75fced36