ext4: Do not reserve free space for root user upon creation

PVCs are data volumes most of the times, and reserving space for system
tasks is probably unnecessary.

The user can still modify a specific PVC's reserved blocks through the
`tune2fs` command.

declarative.py

@@ -61,7 +61,7 @@ def current_fs(device):
 def be_formatted(dev, fs):
     def init_fs(device):
         if fs == "ext4":
-            run(f"mkfs.ext4 {device}")
+            run(f"mkfs.ext4 -m 0 {device}")
         elif fs == "btrfs":
             run(f"mkfs.btrfs {device}")
         else: