Added encryption support for zfs recv -o / -x

One small integration that was absent from b52563 was
support for zfs recv -o / -x with regards to encryption
parameters. The main use cases of this are as follows:

• Receiving an unencrypted stream as encrypted without needing to create a "dummy" encrypted parent so that encryption can be inheritted.

• Allowing users to change their keylocation on receive, so long as the receiving dataset is an encryption root.

• Allowing users to explicitly exclude or override the encryption property from an unencrypted properties stream, allowing it to be received as encrypted.

• Receiving a recursive heirarchy of unencrypted datasets, encrypting the top-level one and forcing all children to inherit the encryption.

Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #7650