Return different error code for the guard page layout violation.

On KERN_NO_SPACE error, as it is returned now, vm_map_find() continues
the loop searching for the suitable range for the requested mapping
with specific alignment. Since the vm_map_findspace() succesfully
finds the same place, the loop never ends.

The errors returned from vm_map_stack() completely repeat the behavior
of vm_map_insert() now, as suggested by Alan.

Reported by: Arto Pekkanen <aksyom@gmail.com>
PR: 223732
Reviewed by: alc, markj
Discussed with: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Differential revision: https://reviews.freebsd.org/D13186