The docker graph call driver.Exists() on initialisation for each filesystem in
the graph. This results will results in a lot `zfs get all` commands. To reduce
this, retrieve all descend filesystem at startup and cache it for later checks
Signed-off-by: Jörg Thalheim <joerg@higgsboson.tk>
Upstream-commit: bad25ccf978b56da6fa181439504ab33906524cd
Component: engine