Corrected oversight in ZERO_RANGE behavior

It turns out, no, in fact, ZERO_RANGE and PUNCH_HOLE do
have differing semantics in some ways - in particular,
one requires KEEP_SIZE, and the other does not.

Also added a zero-range test to catch this, corrected a flaw
that made the punch-hole test succeed vacuously, and a typo
in file_write.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #13329
Closes #13338