xfstests: fix brain-o in fallocate log dump

xfstests: fix brain-o in fallocate log dump

fsx segvs when dumping fallocate log entries. Fix magic string
array index parameters to be zero based rather than one based.

While touching log string related stuff, make the format consistent
with read and write operations so the log dump is easier to look at
with the human eye.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>