After OpenZFS import, zpool auto import behavior was moved to an
an explicit "zpool import -a", and the zpool rc.d script was added
as a prerequisturite of zvol.
However, zvol runs before dumponin rS299839, zvol was added as a prerequisite of dumpon, making it to start very early and before all 'disks' providers. At this time, dumping on a zvol is not supported, soso remove this moved the import to arequirement and make zpool depend on disks instead.
very early time, and in the case the pool is on an unlocked geli
provider, it would not get a chance to get imported.