Fix VERIFY(!zil_replaying(zilog, tx)) panic

The zfs_log_clone_range() function is never called from the
zfs_clone_range_replay() function, so I assumed it is safe to assert
that zil_replaying() is never TRUE here. It turns out zil_replaying()
also returns TRUE when the sync property is set to disabled.

Fix the problem by just returning if zil_replaying() returns TRUE.

Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reported by: Florian Smeets
Signed-off-by: Pawel Jakub Dawidek <pawel@dawidek.net>
Closes #14758