Avoid to run `fsck` twice (and save some time during boot)

[Anton Sayetsky]

2013/12/13 Antonio Kless <antoniok.spb at gmail.com>:
> What do you mind?
>
> Well, first check with "-p" is exactly what I want to avoid before doing
> second check without it.
fsck checks limited range of errors in preen mode. This works really FAST.
Logic is following:
1. Run very fast (preen) check on FS if dirty flag set.
2. If above fails, run full and slow check.

Of course, you can disable preen pass. But be ready to multi-houred
filesystem checks on every unclean reboot even if FS isn't damaged.