zstreamdump -C always fails. It is not calculating the checksums, but
it's still trying to verify that the (non-calculated) checksum matches
the one stored in the send stream.
This change makes zstreamdump -C not verify checksums.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes#9983