Uses finer grained locking so that each volume name gets its own lock
rather than only being protected by the global lock, which itself needs
to be unlocked during cetain operations (`create` especially`)
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Upstream-commit: fe66fdd18c0307cc02e6aeff8625c179452b8436
Component: engine
