Windows: change buf_Find*() signature to accept cm_fid_t

Windows: change buf_Find*() signature to accept cm_fid_t

The buf_Find*() functions require a cm_fid_t to match with the
cm_buf_t objects not a cm_scache_t.  Change the signature so
that the cm_scache_t is not required.  It should be possible to
search for a buffer even if the cm_scache_t is not present in
the cache.

Reviewed-on: http://gerrit.openafs.org/5304
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit c23b27a69322f4c9963a532d5cbcb136b23bb20c)

Change-Id: Ie4546de582e0ffe9103f1bb01e05cf387265da49
Reviewed-on: http://gerrit.openafs.org/6799
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>