libext2fs: zero block contents past EOF when setting size

libext2fs: zero block contents past EOF when setting size

When we set the file size, find the block containing EOF, and zero
everything in that block past EOF so that we can't return stale data
if we ever use fallocate or truncate to lengthen the file.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>