Linux: Remove unnecessary crhold on incomplete kernel credentials

Linux: Remove unnecessary crhold on incomplete kernel credentials

When credentials debugging is active in the kernel, sanity checks
in various credentials functions such as get_cred or put_cred
require that they are called with full fledged kernel credentials.
This can be a problem with recent kernels in osi_Init where we
build our own credentials and try to "crhold" them.
Getting a reference doesn't make much sense anyway since we're
using a statically allocated structure that we never try to free
or modify.

As a minimal fix, just don't call crhold when we're using
the kernel credentials structure.

Change-Id: If4f843ad33526c6a42f1cf67c57763593ffa50ac
Reviewed-on: http://gerrit.openafs.org/1828
Tested-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>