Revert "Assign specific type to metadata block device."

This reverts commit ee94431da41af9f892dc34dcc624c2e78623843d.
Revert "Assign specific types to system and recovery block devices."

This reverts commit 6584ed77ead967dbfcfb0e81e7f4fe0c0a6a6de3.
Manta: DU-ify the tree
Revert "Assign specific types to userdata and cache block devices."

This reverts commit aebc2ea9731a2dcb7c9d40bf5997db308327c32a.