Reduce luksFormat iter-time for slow devices
Since pmos is being built for old devices on modern systems, the number of hash iterations during build time can lead to VERY long
cryptsetup open times on the device.
--iter-time should default to some number of ms (500?) so that opening the luks device on the phone doesn't take tens of seconds. This option should be configurable via a cmdline parameter during
pmbootstrap install so the default value can be overridden.
I suggest defaulting to 500ms for