generic/033: Don't call 'fzero' with the KEEP_SIZE flag

generic/033: Don't call 'fzero' with the KEEP_SIZE flag

None of the fzero calls in this test end up writing past the end of the
file, so this flag is unnecessary and can cause the test to fail on
filesystems that don't implement FALLOC_FL_KEEP_SIZE.

Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>