include: Ensure security/audit/audit.h gets staged properly.

There is a conflict between bsm/audit.h and security/audit/audit.h due
to the way that staging is being set up using .PATH to point to the
full directory and the leaf files being specified in the list. Due to
this, the bsm/audit.h was getting staged as both bsm/audit.h and
security/audit/audit.h since the sys/bsm directory is listed first in
the .PATH list.

Use sys/security in the .PATH instead of sys/security/audit and specify
the audit header files as audit/<name>.h. This ensures that we get the
correct audit.h stanged for security/audit/audit.h.

Reviewed by: sjg
Obtained from: Juniper Networks, Inc.