stages/disks: adds -p flag to mkfs.ext4
stages/disks: adds -p flag to mkfs.ext4

Fix problem where Ignition overwrites existing filesystem when using ext4
regardless of what filesystems.mount.create.force is set to.

AlexNPavel/ignition,ajeddeloh/ignition,dgonyeo/ignition,dgonyeo/ignition,coreos/ignition,ajeddeloh/ignition,AlexNPavel/ignition,coreos/ignition,dgonyeo/ignition,higebu/ignition,AlexNPavel/ignition,coreos/ignition,higebu/ignition,higebu/ignition,ajeddeloh/ignition