Fix incremental recursive encrypted receive
Review Request #2415 - Created Oct. 25, 2019 and submitted
Currently, incremental recursive encrypted receives fail to work
for any snapshot after the first. The reason for this is because
the check in zfs_setup_cmdline_props() did not properly realize
that when the user attempts to use '-x encryption' in this
situation, they are not really overriding the existing encryption
property and instead are attempting to prevent it from changing.
This resulted in an error message stating: "encryption property
'encryption' cannot be set or excluded for raw or incremental
This problem is fixed by updating the logic to expect this use
ZFS test suite was run on SmartOS. In addition, the user that originally encountered the problem (on SmartOS) tested a SmartOS image with the fix and verified the problem went away.