This reverts commit e3b39a677b535bc2676a939519906f6b2dbce6f4.
I misunderstood and thought this was ready to go in the tree, but it was
on a remote branch only for a review.
This fixes having JFS as the root partition on battery power.
For most modern FS's this is a non op, or a very small op by default
so it should be fine.
Fixes Gentoo #291654.