Comment 4 for bug 1763712

Related change: https://review.openstack.org/624809

Dan Smith pointed out in https://linux.die.net/man/5/lvm.conf that by default (locking_type/wait_for_locks) it will lock for concurrent operations to avoid corrupting data.

(2:59:46 PM) dansmith: 1. access to dm is one at a time, IIRC, which means they'll fight to setup dm devices to some degree, and
(3:00:09 PM) dansmith: 2. If they're doing anything that causes buffer cache to flush, two running at once on an io-limited system will slow things down
(3:00:24 PM) dansmith: IIRC, there is a long history of issues with lvm concurrency