OpenBSD: don't use AFS_GLOBAL_SUNLOCK on single processor system

OpenBSD: don't use AFS_GLOBAL_SUNLOCK on single processor system

Put back the header directives that only turns on AFS_GLOBAL_SUNLOCK
when compiling for multiprocessors system. When enabled on a single
processor OpenBSD system, it is possible to put the entire system
into a lengthy (minutes) lock state when performing multiple AFS
activities. The system behaves MUCH better when AFS_GLOBAL_SUNLOCK
is not set (no problems encopuntered). This whole locking mechanism
needs a bit more examination on OpenBSD before this is useful in
single processor mode.

Change-Id: I19813b78ad8d705b4f043ccb3a38c83e278972e9
Reviewed-on: http://gerrit.openafs.org/1276
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>