* origin/pr/354: (35 commits)
tests/lvm: re-introduce POOL_CONF
tests/lvm & callback: remove explicit class references
storage/callback: remove the "word of caution"
storage/callback: comment fixes
storage/callback: add the config ID as callback argument
storage/callback: some callbacks added & removed
tests/lvm & callback: Refactoring
Revert "storage/callback: do not run sync code async"
tests/callback: ensure missing conf causes errors
storage/callback: do not run sync code async
tests/callback: added callback-specific tests
storage/callback: async Volume.export() & added Volume.export_end()
storage/lvm: make the "hack" work with CallbackPool instances
storage/callback: add the backend_class property
tests/callback: add them to the rpm build
storage/callback: various fixes
tests/callback: add rudimentary tests for the callback driver
tests/lvm: make the tests re-usable for other drivers
storage/callback: fix issues detected by pylint
storage/callback: volume callbacks now also rceive the source volume as argument (if there's any)
...