kern/49842: lock assert when reloading opencrypto module

[prlw1%cam.ac.uk@localhost]

>Number:         49842
>Category:       kern
>Synopsis:       lock assert when reloading opencrypto module
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Apr 16 14:25:00 +0000 2015
>Originator:     Patrick Welche
>Release:        NetBSD-7.99.9/amd64
>Organization:
>Environment:
>Description:
loading, unloading, and loading the opencrypto module caused a laptop to spontaneously switch off. Running a LOCKDEBUG kernel on another machine and repeating the experiment reveals:

  Mutex error: lockdebug_alloc: already initialized
>How-To-Repeat:
Build a kernel without IPSEC, hifn, ubsec, crypto, swcrypto and with LOCKDEBUG.

modstat | grep crypt    shows nothing
modload opencrypto
modunload opencrypto
modload opencrypto      panics

(As to why bother - mysteriously trying out opencrypto's compression in a rump kernel, gives a sigsegv in net/zlib.c, but not when running an ordinary swcrypto builtin kernel, so attempted to use modules to ease debugging...)
>Fix: