localfs: use mtime/size/inode for checksum
localfs: use mtime/size/inode for checksum

Currently it depends on the whole `info()` output, which has too much
information that doesn't really matter. To check if file contents didn't
change mtime, size, inode combo is enough.

dmpetrov/dataversioncontrol,dmpetrov/dataversioncontrol,efiop/dvc,efiop/dvc