Make remount into checkpointing for ext4 userdata a no-op

We are going to teamfood userspace reboot soon, and in order to gather
as much data as possible we are fine with ignoring checkpointing for the
devices with ext4 (teamfood will be a very limited set of people that
are aware what they've signed for).

As result of this, we don't need to reset vold and kill zram backing
device. Added a TODO to restore that functionality if needed.

Since I was there, fixed yet another typo in userspace-reboot-resume -_-

Bug: 135984674
Test: adb reboot userspace
Change-Id: I2b7a93aaf738fe9bec9d606d7e11aefb325550b1