Fix metadata location when file system doesn't span the partition

Pad the sparse image with a zero fill chunk to correctly position
verity and FEC metadata at the end of the partition.

Bug: 27073791
Change-Id: I9f70d579a42e5007d50e9c02a98a608d2815f0ed
(cherry picked from commit 6a8781a25113b9b49dddc8c8e043c27d5a943e3a)
2 files changed