tests: rsend.kshlib: cmp_ds_prop: mask out differences in origin pool

tests: rsend.kshlib: cmp_ds_prop: mask out differences in origin pool

This fixes rsend_011_pos:
20:28:26.94 SUCCESS: cmp_ds_prop testpool/testfs/fs1/fs2 testpool2/testfs/fs1/fs2
20:28:26.96 2c2
20:28:26.96 < origin    testpool@psnap  -
20:28:26.96 ---
20:28:26.96 > origin    testpool2@psnap -
20:28:26.97 ERROR: cmp_ds_prop testpool/pclone testpool2/pclone exited 1

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13250
Closes #13259