14.04: thinpool metadata repair is not supported

from https://answers.launchpad.net/ubuntu/+question/253962:

I was looking into how to repair LVM2 thin pool metadata and noticed that Ubuntu ships with LVM2 tools 2.02.98-6. In 2.02.98-9 (in Fedora), the option to swap a thin pool metadata device was added: Add lvconvert support to swap thin pool metadata volume -- https://apps.fedoraproject.org/packages/lvm2/changelog. It's also present in the 2.02.99 release of LVM2 itself: http://upstream-tracker.org/changelogs/lvm2/2.02.99/changelog.html.

Without this option, it's difficult (I can't figure out at the moment how, exactly) to take a thin pool metadata device offline to perform metadata repair. Would be great to include a fix for this in Ubuntu.