bypasscache for ukernel

bypasscache for ukernel

simple (read) bypasscache for ukernel.
does not bother trying any buffercache stuff.

Reviewed-on: http://gerrit.openafs.org/5484
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit d1cf14d54e380014851fb850b65263a66a8a4443)

Change-Id: Ia66dcdfad42fe95b3456430eeb8b12c161c185a5
Reviewed-on: http://gerrit.openafs.org/5561
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>