Windows: Ensure pResultCB exists before Authentication

When processing requests from the redirector it is possible for
the ResultCB to not be allocated.  This can occur either due to
an out of memory condition in a synchronous request or due to
an asynchronous extents or byte range lock request.

Move the assignment of the Authenticated state after the allocation
of the ResultCB from the stack in case of out of memory conditions.

Change-Id: I7e98edde712b532010aa15705a62cf91dd9d0ebf
Reviewed-on: http://gerrit.openafs.org/9110
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>