generic/092: skip test if file allocation unit isn't aligned

generic/092: skip test if file allocation unit isn't aligned

This test exercises allocation behavior when truncating a preallocated
file down to 5M and then up to 7M.  If those two sizes aren't aligned
with the file allocation unit length, then the FIEMAP output will show
blocks beyond EOF.  That will cause trouble with the golden output, so
skip this test if that will be the case.

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