OpenZFS 7071 - lzc_snapshot does not fill in errlist on ENOENT

OpenZFS 7071 - lzc_snapshot does not fill in errlist on ENOENT

Authored by: Igor Kozhukhov ikozhukhov@gmail.com
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Ported-by: George Melikov <mail@gmelikov.ru>
OpenZFS-issue: https://www.illumos.org/issues/7071
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/25f7d99
Closes #5597