I'm pretty sure your only option is to delete the disk group and recreate it. If the pool, that the vdisk is in, has multiple disk groups then the system will attempt to drain the disk group to other disk groups in the same pool but benefit is that your pool stays online. This can take a while. After it is drained, you can recreate your group.
If there is not enough space in the pool to drain the disk group out then the command will fail and you'll need deal with the whole pool. If you have Pool A and Pool B then you could always look to do a host-side copy of the data to volumes housed by the other pool.
Or, if you just don't care about the data on the system then just go nuclear on the vdisk/pool and you should be good to go.
Since this is an MSA 2050 you likely have support on it so you could always log a case and see if support can identify a way to do this without deleting the vdisk but I'm not aware of a way off hand.