e2fsck: fix incorrect interior node logical start values

e2fsck: fix incorrect interior node logical start values

An index node's logical start (ei_block) should
match the logical start of the first node (index
or leaf) below it.  If we find a node whose start
does not match its parent, fix all of its parents
accordingly.

If it finds such a problem, we'll see:

Pass 1: Checking inodes, blocks, and sizes
Interior extent node level 0 of inode 274258:
Logical start 3666 does not match logical start 4093 at next level.  Fix<y>?

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>