2049 env(1) should print program it attempts to exec on error, not argv[0]

2049 env(1) should print program it attempts to exec on error, not argv[0]
Reviewed by: Dave Pacheco <dap@joyent.com>
Reviewed by: Dan Kruchinin <dkruchinin@acm.org>
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Reviewed by: Jason King <jason.brian.king@gmail.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Albert Lee <trisk@nexenta.com>
Approved by: Eric Schrock <eric.schrock@delphix.com>